Man you are better than most car shows out there Alex! I learned a lot more with you than those flashy television programs. Keep up the good work homie!
So the difference is audi and subaru always send some power to the rear wheels? We have snow/ice races here in Alaska and the subaru's and audi's always win. The 4matic and Xdrive always shut on and off it's like they are confused on the ice. How do the Lexus RX 350 AWD work? Is it FWD based until slippage occurs? They should use the Audi's AWD or Subaru it's better. I bought a Subaru Outback for my wife it feels like it's on rails in the snow. I want to get her a Lexus RX but if it's not better AWD system then I will buy another Subaru. RAV4 AND CRV should not be allowed to be labeled AWD they get stuck in light dusting of snow. Thank you Alex for taking the time to explain these systems. Let's see the new Outback and Forester reviews!
Awesome video and great information. I'm thinking about getting 2015 Subaru Outback, and have visited 2 dealerships to find out details about the vehicle and the difference between 4wd systems for the CVT and 6-speed manual. At one the salesman said they are the same systems. AT the other the salesman asked 2 other guys, and then went to check with a mechanic to get very limited answer. Your reviews rock. Big props for the detailed info.
I enjoy almost all reviews on youtube, but yours are the most informative and useful to me. Clear and direct without an obvious bias, or if there is you say you have a like for a particular car. And your explanations of the mechanics behind the running of the cars is informative and understandable. Keep up the good work. Thanks
Great vid! Probably the most concise and understandable explanation I've seen in a while. One note, related to your last comment... it's more than just how the computer is programmed. One also needs a rear differential and a center transfer mechanism that can handle more power. One car manufacturer in particular, started marketing their limited duty AWD system more aggressively into the off-road segment, and ended up having issues with burnt out rear ends from things as simple as beach travel. If the clutch packs and rear end can't handle the necessary power, bad things happen. ;-)
As an Impreza freak and proud owner of a 23G ice blue WR1 (one of only 500 released in the UK), this was a great explanation of why my beloved car can cut it in adverse conditions even with low profile, non-chunky tyres. I don't race around in it like a dick and knowing how to drive in all weathers helps a lot. I am mostly an idiot re what's under the beautiful exterior. Thanks you!
Torque split depends on the transmission, model, and year. For example, Gen 3 Outbacks have ~41/59 Front/ Rear. Gen 2s (and the Baja) were mostly 45/55. Imprezzas are all over the place.
Really enjoy your channel a lot. All other automotive reviewers out there: TV, magazines, RUclips included loves to rave and kiss a$$es. You have always been very clear of your personal unbiased views. Not only that, you have demonstrated you have thorough knowledge of automotive engineering. To top that off you are a consummate presenter also. You are an excellent editor or do you do all of your videos in one shot?
I believe another advantage over other "slip 'n grip" systems is the fact Subaru's AWD has torque vectoring and can send most if not all power to just one wheel. In extreme cases should only 1 wheel have grip, it's been proven than Subaru's AWD can pull a car uphill with just one wheel, where most other AWD systems fail. Subaru doesn't mess around. It's the best and most practical AWD system out there, I feel.
Hey, great presentation! I've been reading about the workings of Subaru AWD off and on for years, but there are a few lingering mysteries that none of the sources address. What is it about the type of transmission that dictates the type of AWD system? Why does it makes sense, from an engineering standpoint, for manuals to get a viscous coupling while automatics get the multi-plate clutch? It seems there must be some mechanical reason, or else it would make economic sense for Subaru simply to deem one system "better" and use it universally (other than special cases like the STI). And if the MPT, under normal conditions, is sending some power rearward without locking completely, doesn't that mean the clutch plates are usually intentionally slipping a bit? How does that not quickly wear them out?
manual Subaru's have a center differential in conjunction with the viscous coupling. A system with only a viscous coupling would only send power to the rear when the front are spinning
Alex - I am looking at two CVT SUVs. I put a lot of miles on my car for business, something like 20,000 a year at most, 15,000 a year least. I am concerned that the CVT transmissions won't last beyond 100,000 miles before needing major overhauls. I currently drive a Jeep Commander with almost 200,000 miles on it and with no issues with the German made TipTronic 5 sp automatic transmission and Jeeps QT-1 all wheel drive system. Can you shed any light on the long term reliability of these CVT units? My thanks.
Alex, can you explain how the current Hyundai and Kia awd systems work compared to others with pros and cons. I believe that the HTRAC and Dynamax aren't slip and grip systems. How do some systems work better on road or off road and how transmissions make a difference as well. CVTs and DCTs can overheat off road I understand.
That is correct. What Subaru hasn't said however is how the clutch pack is programmed. They would very easily program it to deliver a near 50/50 power split which I would say is very likely.
True, there is new "Marketing speak" for Active Torque Split Symmetrical AWD. with emphasis on the "system can send additional torque to the rear wheels either pro-actively or in response to slippage at the front wheels." I'm guessing there are still some form of embargoes on the reviews for both Legacy Sedan and certainly for the '15 Outback.
Isn't Subaru's ABS system playing a significant role in torque distribution? I drove an Impreza for a week in icy town and road conditions and was impressed at how the brakes were quick to slow the spinning wheels, compared to my '12 Rav4 for example.
Forester Manuals are 50 50 split Normal driving. There is no front wheel Bias. The Manuals have a true center diff, the vicious coupling only come into play if there is slipping
I've been a Subaru driver for most of my driving life and there really is no substitute for their AWD system and winter tires. I've driven other AWD cars and as silly as this might sound. There is a reason why Subaru used the liquid to semi-solid system rather than computer controlled systems. Don't get me wrong all cars should have some sort or AWD system especially with the silly amount of HP that most cars seem to have these days.
great video, today I jacked up my 2011 outback 2.5 in the air. I shifted to D gear. but only front passenger side and rear driver side wheel spin. is that normal?
Got a question. what are front and rear differential types? I watched a video from subaru and it says that they shift power front to back(which I get it bc you explained it here) and also side to side. With front or rear differential being open, how does subaru achieve side to side torque distribution? Maybe they are not open diffs?
Excellent description, learnt a lot. My question has a strange twist, I know the basics of AWD and am verse on 4WD, so I know the technical differences. I am looking to get a more family oriented vehicle which would be the Forester. But I want to know from a practical aspect, for light to mid offroading, say beach and camping, how would the Subaru AWD systen compare to say a Vitara with which is a 4x4 with high and low range. Thanks..
Visesh Lall In general, systems with a low range lack a true center differential (note, this is a generality since some systems still have one) which means that the front and rear differential inputs are locked together. This means that even if one axle has zero traction you can still move. In addition you would have the torque multiplication benefit of the low range for steep obstacles or more serious log/rock climbing. The Subaru system was not intended to be a rock-climbing kind of system, it is intended more for dirt, mud, gravel, sand, etc.
I'm confused, from what I know the the CVT models have viscous center joint with no Differential and Manual has Third differential and locking clutch pack.
sam henderson Tricky one. The Subaru system always sends some power to the rear axle, usually it is about 40%. The Acura system will normally default to more of a front bias unless slip happens or you push the car harder. Pushing the SH-AWD system harder it is possible to send 90% of the power to the rear without slip. The Subaru system (2015+, most models) can only split power 50/50 unless there is slip, so there's a sort of rear bias under power in the Acura system. Also Acura employs a torque vectoring rear axle which can send power left and right with or without slip, this is much more capable in terms of handling than an open differential like you find in the Subaru. They are very different systems with different missions. The Subaru system is less expensive but very capable and has a good feel in snow. The Acura system was designed to improve the driving dynamics of their vehicles to make them feel more like RWD drivetrains.
No because Acuras are FWD and cant do a 50 50 split w/o a locking dif. thats why Subarus have a locking dif in Outback and foresters. WRX Sti are still 50x50 and is the Crossteck, the cars that dont have the lock are 60x40. But the models with out the locking diff will resort to 50x50 upon demand as with the Outback and Foresters with out the locking diff.
Thanks for the lucid video. I wonder if you can help. I am trying to diagnose a ticking sound coming from the bellhousing area of the drive train on my 97 Subaru Outback. When running at high speed, the tick in inaudible, except on deceleration. The sound is most pronounced at idle. Listening from underneath, the sound appears to come from the bellhousing area.(The car is AT) From the area of the flywheel that is visible, the flywheel appears to be burnished in comparison to that of my other 97. I thought that maybe a stone or something found its way into the bellhousing because there is no cover for that space. (If the stone were trapped, centrifugal force would keep it stationary at high speed.) I made a chalk mark on the balancer and manually rotated the crank. A pronounced clink occurs at the same spot with each rotation. I had a friend rotate the crankshaft while I lay underneath. The sound came from the transfer case area on the driver side. When the crank came 360 degrees from my mark, I got the same sharp click, like a drop. At 180 to my mark, there was always another barely audible click. (like something re-setting at 180 and dropping at 0/360. I should mention that the car drives well with no signs of diminished function in any area.
Are all the torque converter bolts tight? Otherwise it could be many issues, bad torque converter, something wrong on the input shaft of transaxle, whatever. I'd check bolt and then have a transmission shop familiar with Subaru look at it.
I have a 2011 impreza 2.5i wagon auto for my work car. I live in the mountains and get alot of snow on our interstates before they plow. I bought it used right at the end of last winter and only got to drive in snow once. if i remember right it wanted to fish tail. is that because of my torque split? or could it be bad tires or the light weight of the wagon in back?
Wow! Great explanation; very easy to understand. I've always wondered how Subaru's system differed and now I know. Just one quick question: how much maximum torque can the Active Torque Split system send to the rear wheels?
Because of the design it depends on what wheels have traction. If all four wheels have traction, then the maximum would be 50/50. If however one of the front wheels had zero traction, the system could send nearly all the power to the rear (90%+) until the front wheel(s) regained traction.
***** The system uses an open differential front and rear so the power split is around 50/50 unless slip occurs. If slip does occur then the brake-based traction control system would step in to slow the spinning wheel down. Torque would still be around 50/50 because the brake system does not "stop" the spinning wheel, it attempts to slow it down to spin at the same rate as the other wheel therefore keeping the power in balance.
I have had a Subaru forester 1997 (automatic) from new (approx. 70,000 miles on the clock), that has been great for all the years with very little to do other than annual services. However, recently I have had a lot of vibration & shuddering on the wheels when making slow tight turns (left or right) but never on the straight. It is difficult to identify which wheels the noise or shudder comes from and I don't feel much through the steering wheel. I have had all differentials replace that has reduced the frequency but not eliminated the problem. We hope it isn't the automatic gear box but has anyone got any ideas what to do next.
18 feb 2019 7:48 am est: '(1)Low Power Steering Fluid: 1 of the most commonly seen reasons for a shudder during turning is low power steering fluid. If the fluid level is low, the power steering rack and pump don’t have the right pressure to operate. It could also indicate a leak somewhere in the power steering system, which will need to be inspected. (2)Failing Power Steering Pump: If your power steering pump is beginning to die, it could very easily cause these symptoms. As the pump fails, it produces less and less pressure for the power steering system, causing vibrations, shudders, whining noises and more. (3)Kinked/Blocked Power Steering Line: You need clear power steering fluid lines to ensure the right fluid and pressure distribution. If a line has become blocked or kinked, or is leaking, it can reduce fluid pressure and flow. (4)Failing Wheel Bearing: While its most common to experience a roaring noise when a wheel bearing is beginning to fail, they can also cause vibrations that some drivers interpret as a “shudder”. (5)Failing Differential: If you have an all-wheel drive vehicle, it may be a problem with the front or center differential. When these begin to fail, they will create a shudder, particularly under the stress and strain of a turn.' in www.yourmechanic.com/services/car-shudders-when-turning-inspection from google(tire vibration during turning)result 2
HI Alex.. great video. i have question. I have 2014 Forester, installed 235/60 R17 yet the spare wheel is the original factory wheel which is smaller in diameter, if I install it, well the AWD light flashes? if so, will it damages the transmission?? I saw some video people install a fuse in an empty slot in the fuse and the FWD light comes on, I tried all empty fuse slots, the FWD light never came on. appreciate your kind advise.
Ok so I have a 5 speed 09 outback xt. I watched the guy from Engineering Explained go through all the subaru awd systems and I could understand why the ones for the sti and wrx were designed the way that they were, but I don't understand why the manual and automatic here are different? Is there a reason why the manual transmission subarus Need to have the viscous coupling setup vs what they have in the auto or is it just something that subaru did randomly? Is it because they think less people buy the manual versions anymore /or they don't make them entirely and so they see no need to update the mechanics in those models?
The picture at 1.24 is incorrect. 1st the engine is very low and wide and the drawing is spot on but it should be rotated 90 degrees. 2nd the gearbox is pretty long and starts where the windscreen is and goes all the way to the backside of the front seats, which means that the actual driveshaft at the back is pretty small -) Next time provide the pics of the car and gearbox! Another thing to mention is that the TZ gearbox provide 90% to the front and 10% to the rear as a normal drive and able to shift to 60/40 if needed, also in the manual mode (1st gear) they can operate at 50/50...
I have an 03 Forester, at a complete stop on slippery snow road, when I accelerate the front tire spins in the snow then about 1 sec of spinning the awd engages, is that normal?
U should have explained how it transfers torque from front left to front right!does it have a EBD using open diffs and ABS or has it got some diff locks but overall the movie is good!
Hi, I have a couple of questions. Is the multi plate transfer clutches in a oil bath or something?! What is preventing wear and tear of the clutches? Can they overheat and if yes, is there usually some sensors for that? I read elsewhere that the CVT in the 2015 Outback (and others) is not designed for engine braking. Downshifting with the paddles will increase wear and tear on the CVT. Is this true? If you are for example spinning on ice and suddenly "catch" some tarmac, what is preventing the shock from destroying the CVT cones due to slippage? I recently tried a Outback 2015 - the electronics limits the RPM to prevent strain to the CVT (as I understand it). I am unable to climb steep hills and even a simple diagnoal test (uphill) caused the outback to simply not move at all. I wonder how weak/strong is the outback in case of towing a trailer uphill (especially when starting). I supposed you can't add much weight when the car is incapable of moving itself without load. I live in Norway so the only Subaru I would consider buying is the Outback 2015 2.0 diesel. More details on this is appreciated :) (thanks for a nice principles of operatoin explanation).
Svein Engelsgjerd Yes they are a wet clutch design. In theory any wet clutch like this can overheat, Subaru helps prevent this by using more plates to reduce the load and improved cooling. The CVT doesn't have any durability issues when downshifting per se, no more than in normal operation. Slip is unlikely in those situations because of the belt design, but as you noticed the low end ratio is not very low and that is the limiting factor on steep grades or towing.
+Alex on Autos Hi and thanks for answering. I do have a few follow up questions if you don't mind. 1. Wet clutch design: Does this particular design rely entirely on the viscous effect or is there actual friction involved between the plates? 2. Slip of the CVT belt. Is not the belt design exactly the reason it can sllip? If a belt is on two smooth surfaces - is it not likely that the belt may slip if the car suddenly snag in the tarmac?. I realize of course that the energy would have to go from the tires, through the rims , through the differentials and so on before it ends up in the gearbox (which does have the converter (with clutch?) that also dampen the shock a bit). Regardless I am concerned about this.
Svein Engelsgjerd There is friction between the clutch surfaces, this is not a viscous coupling like in the Subaru manual transmission. The belt is a steel belt design that is not exactly smooth per se, but by its very design it really doesn't slip like tat, any like forces would probably get absorbed by the torque converter.
Regarding the clutch pack again: On Subaru's website the outback is claimed to have a 60/40% split between the forces. Would not this mean that the clutches are "mostly engaged" ?! I am sure it works, but logically it sounds like they are prone to wear and tear - especially if used often. On the other hand normal dry clutches is (very) hard to wear out unless they get hot. Is there a heat sensor/monitor/estimator for new outbacks so you know when to relax/wait a little?
Svein Engelsgjerd There is wear involved as with any clutch but it should be very long term. There is a temperature sensor but it is the transmission's sesnor since the AWD and transmission are both inside the same case.
How does Subaru send all the power to one wheel if it has a traditional rear end? I thought I've seen a video showing a Subaru on rollers where one wheel had traction and it climbed up.
+boostedmaniac Traction Control. If they sense a wheel slipping, they'll lock the brakes on that 1 wheel. If you watch the one-wheel traction videos closely, you'll see loose wheels jerk and stop when the car pumps the brakes to get traction.
I'm confused... 1. I thought the transfer case is what separated AWD from 4WD. 2. Do both Subaru's automatics and manuals use the same power distribution method? 3. If power distribution is almost always 50/50, doesn't that cause problems when turning?
Peter Schmidt 1. Once upon a time it was, but now the waters are very murky. 2. No, they are different. Most CVTs use a multi-plate clutch and most manuals use a viscous coupling. 3. The viscous coupling allows power to flow approximately 50/50 without actually having them bound together which allows you to turn without binding.
In our 2013 Outback 3.6R (traditional tranny) I've been under the impression that the split is rear-wheel-biased 45/55 (front to rear). Is this referred to as Variable Torque Distribution on my particular model year? Am I correct or did I miss something while doing research? By the way, great explanation on the AWD system. The following is copied from SOA website: Variable torque distribution AWD: An AWD system designed exclusively for 5-speed automatic transmission, E-5AT (with manual mode) models to provide aggressive, sporty driving with increased turning abilities all while retaining the fundamental driving stability offered by the Symmetrical AWD. An uneven 45:55 front and rear torque distribution has been set for the front and rear tyres. Sending greater torque to the rear wheels can reduce understeer, a trait that plagues 4WD vehicles, when cornering for smooth and agile handling. Torque distribution is controlled automatically up to an equal 50:50 front and rear to suit road surface conditions for both sporty driving and stability.
Because you have a 2013 model, you are correct. Subaru made a change to the 3.6 L drivetrain in the latest generation. The current model with the 3.6 L engine does not use the Torsen centre differential any more.
Alex on Autos Thanks Alex, I've owned my 13 OB for almost 3 years and have found the AWD system (very effective) but very confusing. You've definitely cleared it up for me. Thanks again.
The CVT 3.6r have locking diffs. for starting 50x50. If you are in motion and your in snow, or climbing, in mud, rocks, the CVT will split 50x50 and send power to the wheels with the most grip... FWD cars cant do this. Jeep, and Tacoma owners spend thousands to get the same grip Subarus get.
Sorry, didn't get it, speaking about Subaru Outback 2015 model year (new gen) what system 2.5 has, what 3.6 has, are they different? Are they 60/40? Is for Forester the same? What is better viscous coupling or multi plate clutch and why? Thank you for the video!
They are different, not better really. The 2015 models with both engines and teh CVT use the multi plate clutch and a 60/40 bias, manuals use the viscous coupling and a 50/50 split.
Alex on Autos Thank you for your response! What about CVT, as I understood from Subarus materials - Outback 2015 has latest generation of CVT and 3.6R model has more heavy-duty version. Is it really new? Maybe you know what did they improve?
Jack Tomson There were only minor changes to the CVT for the 3.6R model and the changes were mainly to help it handle the increased power output from the larger engine.
You're telling me the manual transmission subaru never has a 100% direct connection to the rear wheels? If so... that explains a hell of a lot of why the car feels "dead" and "souless" compared to other MT car's I've driven. I was wondering wtf was up.
How is it that the clutch packs of other manufacturers (like Nissan) tend to overheat even though they are rarely engaged yet Subaru's never seem to overheat even when flogged, and is always engaged?
It is all in the design. By putting the clutch pack into the transmission case it can take advantage of the transmission's active cooling system. When clutch packs are on their own they don't have a radiator to help dissipate the heat.
Great Video. But I own an 2014 Forester with the cvt. So let's say I'm in a slippery condition. You're saying that my car would have 60/40 split instead of 50/50 ?
I am confused. In my 2013 forester manual 5 speed the AWD system works like the 4WD system on my truck... power to the front left tire and rear right tire.. difference being 4WD has locked hubs with a LSD or a locker in the diff.. AWD having open diffs using the same setup but computers monitor wheel slip, if slip is detected it then redirects power to the opposing wheel through a clutch pact. I have performed many tests on ice and proved that is how my system works.. the power split on my Subaru is 41-59 and if needed it will do 50-50.. I have never experienced a situation where my power split was 60-40.. the front tires usually do not slip first except if the front tires have no traction but rear tires do..It is always the rear tires that slip first for instance on a frozen lake or a sheet of ice at a intersection the majority of the power goes to the rear and the rear kicks out until the front wheels have caught up in wheel speed. While I am cornering I apply more power and the rear kicks.. If what you are saying is true about 60-40 split then i should experience under steer or feel the front slip during hard acceleration right? Am I misunderstanding something? How I have felt the car drive and what you are explaining do not match. Did Subaru change their design between 2013-2014? Even a certified Subaru mechanic has explained to me that my forester has a rear bias and if needed can even the power between the front and rear but never front wheel bias. Now other vehicles i have driven that have a setup such as the CRV I for sure felt under steer while cornering and front wheel slip during hard accel... which would make sense that the CRV has a 60-40 split. But I have never felt under steer in a Subaru cause of a front power bias, if under steer happened it was the drivers performance.. I bought Subaru over Audi, BMW, Honda, Acura and all the other companies selling AWD because I was told the Subaru AWD was not a front bias setup. Last thing I might add is I have a controller that allows me to manually choose power between front and rear.. like what you find in the WRX STI.. I can never do a 60-40 split. It is always between the range of 50-50/21-79. But even on my buddies Forester without the controller he still has a rear wheel bias. I appreciate the video, I would love to hear back from you with your thoughts.
+duuane cooper Subaru is always updating their systems. What was the norm in 2013, they completely change by 2016. They offered low range gears well into the 2000s Foresters and Outbacks in some markets. Granted it wasnt terribly LOW for a low range, but it was better than regular hi range gears. V
+Y10Q thank you for the reply . I simply love what Subaru does. I'll be coming to your channel later if I have some questions about newer models. Thanks!
So in a 2005 WRX it has the viscous transfer case behind the transmission, but you said they program it to be 50/50 by default? I wanted them to do that AWD test on an "older" manual transmission car but I just can't find it.
Well with a viscous coupling there is no programming per se. The coupling has two sets of plates that alternate ABABABABAB. The As are the input the Bs are the output. Assuming that the front and rear are spinning the same rate, the power flowing through the coupling can be 20-50% or so depending on the exact design. If however they start spinning different rates, the fluid becomes more viscous and the coupling "connects" more aggressively. There will always be some slip, but a 90%+ transfer is fairly common.
On a side note, do you know how Mitsubishi does their AWD system? All I can gather from what I am able to find is that all their differentials are electronically controlled by a computer that senses what tires need the grip, nothing specifically mechanical.
Jeremiah Yareff If you are referring to the Lancer EVO, then early versions uses a viscous coupling but since about 2001 they have been using an electronically controlled multi-plate clutch pack that not only reacts to wheel slip but allows the computer to deliberately allocate power to the rear at various levels.
Thanks for the reply. Very quickly too. So with that system (all it has is ABS I think, and just the drive train) is there any control to left or right wheels, or is that purely the differential (needing to be partial locking to do left to right)?
Subaru sends 60 x 40 since 2016, to increase fuel economy. Prior models are 50 x 50 like my 2012 Outback 3.6R and its how you get the best traction. Technically Subaru's are Rear Wheel drive up to 2016 or 2017 where they split 60x40. What makes a FWD is the Transverse engine either, 4, 5, 6, 8 cylinder engines... Subaru does not have a FWD engine but a flat 4 or flat six similar to a v4 or v6 that can produce more torque with the power it has. People should stop comparing Subaru's to FWD cars they are not the same at all...
hello i have a 2007 forester 2.5 non turbo automatic, the locking solenoid seems to have all the wheels locked, i have a grabbing feeling and rubbing sound when making turns, no transmission or abs codes, any advise would be greatly appreciated
I'm not expert on these but worked on cars many years. Are you saying that without any lock button engaged, the solenoid appears to stay on to lock system and you get that abnormal sound? Appears if you are using the lock button you need to turn it off, as its only designed for use in extreme slick conditions like if you're getting stuck or something. If its turned off, have a shop look at it as if its engaged on its own, you will wear out drivetrain / tires or both, as the back tires are supposed to turn less around turns than front due to the arc of the turn, and forcing them to turn same rotation binds up drivetrain.
EGGINFOOLS The Subaru system (most models) uses open differentials front and rear, so there is no ability to do that beyond the brake-based traction control.
Hi Alex, just out of curiosity, which AWD system is the best for winter driving between Subaru's, Acura's SH-AWD and Audi's Quattro? Would it be reasonable to say that they are about the same?
For winter driving Quattro or Subaru would be the better choices because both systems send nearly 50% of the power to both axles (longitudinal Quattro only) while Acura's system is 90% front when starting unless there is slip or you're driving the system hard. This results in the Subaru and Audi delivering a more sure footed feel from a stop.
People have hooked up data loggers to Subaru's ECU and have found that the clutch fully locks under acceleration from a dead stop and slowly unlocks as speed rises unless other conditions command more locking. It also showed that clutch lock up in response to slippage is more aggressive the slower you are going.
Are you sure that 60% front/40% rear applies to manual transmissions? I know my 01 Outback manual is 50/50 in all conditions. That said, there is one downside to having the transfer case built into the transmission: If you experience binding in the transfer case, you can't simply replace that part. You have to replace the entire transmission. I've gone through two because of failing transfer cases. (I know I should have sold the car after the second one died but for reasons I can't get into here I can't simply get rid of it).
I currently have a bad driveline in my 05 outback manual transmission I'm wondering if I can run it without the rear drive line maybe half of the driveline can anybody out there tell me if it will work or if I will hurt them clutches
I have never cared that much for the 6. The power output isn't much better than Subaru's turbo 4, it's honestly not much smoother but it does add a decent amount of weight to the car. Personally I think I'd get the naturally aspirated 2.5L engine however. It's going to be the lower cost to operate, maintain and repair in the long run.
1+ on the naturally aspirated 2.2L or 2.5L after 2009. Don't consider the turbos if you're in cold weather. Way more maintenance. and I think 2002's-2008/2009 the outside headgasket will leak like clockwork somewhere between 110k-70k miles. Even when you put a new one on, unless you use the fancy multi-layer steel gaskets which I guess for the cost difference, no one uses. Usually you'll get lucky and the gasket won't leak on the inside of the engine which is better though.
The WRX uses a different style "transfer case" inside the transmission housing. The power split for 2015 is 41% front and 59% rear and this is combined with a limited-slip helical front and Torsen rear differential. The whole package is quite a step above the standard Subaru system.
Alex, you're saying "power" when I think you mean "torque." Perhaps define those two terms upfront and use an example that the torque any wheel can receive cannot exceed what traction it has, and that power = torque x speed. I think also the location of key components is not relevant to the theory of operation, despite Subaru's marketing. Best to define the terms, define the typical components, discuss the theory of operation using those components in the various models, then describe where components are located in Subaru's implementation. Thanks for your efforts!
+cobra454tim they use Torsen on Tribecas and Outbacks, drawback is that when it breaks, you gotta stop and fix it. It is a mechanical system. You can't drive it. When a viscous system breaks down, it acts as an open differential and you can drive it like that forever or till you notice that you have an open diff
The new Legacy uses the same AWD system on the 2.5 and 3.6 models (in 2014 they used different systems). It uses a multi-plate clutch pack to distribute power front/rear. Under normal conditions power is 60/40 F/R.
Alex on Autos Awesome thank you for that information. Very informative posts which are greatly appreciated. Correct me if I am wrong but that means the Legacy is capable of transferring 100% of power to front or rear if needed and left and right..?
Kamber Bulica Well it depends on how you look at it. If no wheel slips, then the system will vary from 60% front to 50% front and each tire will get 25%. The system is not capable of sending more than 50% to the rear or more than an equal share side to side unless there is slip. IF a front wheel slips, the system can send 100% of the power to the rear and if a rear wheel slips 100% can go to the front. No version has torque vectoring in a mechanical sense so power is essentially equal across the front and rear axle (L to R).
I have a 2014 Forester, and I must say that after having a 2001 CR-V SE 4WD for almost 12 years and selling that for the Forester last year, the Forester is a lot better with its Symmetrical AWD system. About power distribution, certain Subarus, such as Tribeca, WRX, and WRX STi, send power about 40% to the front and 60% to the rear.
This video is limited really to the 2015 product line excluding the WRX and WRX STi. (The Tribeca is gone). The WRX uses a different style "transfer case" inside the transmission housing. The power split for 2015 is 41% front and 59% rear and this is combined with a limited-slip helical front and Torsen rear differential. The whole package is quite a step above the standard Subaru system.
I don't think the 'steady-state' 60:40 distribution of torque is correct in the CVT models. I also think you give too much credit for the prowess of the Subaru AWD system currently sold. Their system *is* better but mostly due to better control modules than anything else. I believe the torque distribution is more like 90:10, but continuously variable, so up to 50% can be sent to the rear. Unfortunately, I don't think Subaru is officially sharing this info with us. Also, your description of slip-and-grip systems is somewhat outdated as many manufacturers have move also to a continuously variable distribution. For example, the new CX-5 and RAV-4 are dynamically changing torque distribution as well. You are right that the Cherokee, when properly equipped, has a superior AWD system. Subaru's system is much more similar to the RAV-4, CR-V and CX-5 than to the Cherokee.
I questioned the numbers and Subaru confirmed that much like Torsen center differential vehicles the current CVT system sends 40% of the power to the rear most of the time. This is actually apparent in icy conditions as there is no reaction time in this system. Compared to the CX-5 there is a big difference where there is noticeable front wheel slip prior to engagement. The RAV-4 in its current generation is a 100% font under most circumstances system although you can command the clutch to lock up under 25 MPH by pressing the lock button.
Alex on Autos Torque split varies on subaru models but I think the main trick of the Subaru MPT AWD system is smart programming. I would be hard pressed the find the source but I recall reading about it and here is what I recall. Subaru advertises their system as proactive and it's true. It is mostly but the programming differs on various models of cars however some basic ideas of it's 'proactive opration' are: When the car is starting to move from 0 to up to speed the MPT is locked for 50/50 split. So you always start with full lock as you pick up speed the system progressively decreases the MPT pressure where around 40km/h or it's mostly FWD. If you start pressing the throttle the system will immediately start locking to whatever ratio is determined by the ECU but the main point is that it doesn't wait for slip it reacts to your throttle and progressively locks up the MPT as the ECU programming dictates. The system will also react to wheel slip of course if it determines the axles are spinning at different speeds it will lock up the MPT and that difference is very very small so the MPT locks up quick to transfer torque to the opposite axle and to prevent wear on the MPT. Under no condition does subaru system allow a large speed different between axles because if such an event were to occur it would likely destroy the MPT system so if the ECU detects large different between axles it will actually disengage the MPT completely throw an FWD warning light on the dash and obviously not engage the system until a reset. This is the system present on my 05 4EAT legacy and probably most other basic 4EAT cars. I know WRX and STi use a different system with planetary gear sets in the center diff and all kind of other fanciness to give them varying static split ratios that the driver can control. But even the basic system Subaru has created is excellent especially when paired with an LSD in the back and/or front. It really is great. You have AWD when you needed and none when you dont.
sigsegv0x0b This has changed for the CVT Subarus according to Subaru. The CVT equipped models do not have the clutch pack at full lock from a start in current models, it is a partial engagement allowing for about 40% power transfer to the rear. They also claim that at higher speeds the current models maintain this split rather than biasing to the front.
Alex on Autos Thanks Alex for the update! If the split is 60 front 40 rear on steady-state highway driving and if they use wet mult-clutch plate, how does the fluid not get really hot from the energy lost to friction and how do they maintain good fuel economy in the process (I really don't know, not a trick question)?
David Lee That is an excellent question, and one to which I have never received a satisfactory answer to. There is always energy lost to friction of course, but that also happens in viscous couplings. It is my understanding that the fluid used has properties that lie between traditional clutch pack lubrication and a viscous coupling. This allows some shear forces to transfer from plate to plate even if they are not fully coupled, then of course it can still lock completely. There are a few other vehicles that use a similar "friction additive" like the Jeep VariLock couplings of yester year. In general these just rely on convection cooling, which appears to be OK but I have always thought that some form of external cooler would be required.
This is by far the best explanation of this system...
Thank you, I truly appreciate it.
Man you are better than most car shows out there Alex! I learned a lot more with you than those flashy television programs. Keep up the good work homie!
So the difference is audi and subaru always send some power to the rear wheels? We have snow/ice races here in Alaska and the subaru's and audi's always win. The 4matic and Xdrive always shut on and off it's like they are confused on the ice. How do the Lexus RX 350 AWD work? Is it FWD based until slippage occurs? They should use the Audi's AWD or Subaru it's better. I bought a Subaru Outback for my wife it feels like it's on rails in the snow. I want to get her a Lexus RX but if it's not better AWD system then I will buy another Subaru. RAV4 AND CRV should not be allowed to be labeled AWD they get stuck in light dusting of snow.
Thank you Alex for taking the time to explain these systems. Let's see the new Outback and Forester reviews!
This is among the very best, easy to understand, short and to the point explanations about Subaru's AWD system.
Awesome video and great information. I'm thinking about getting 2015 Subaru Outback, and have visited 2 dealerships to find out details about the vehicle and the difference between 4wd systems for the CVT and 6-speed manual. At one the salesman said they are the same systems. AT the other the salesman asked 2 other guys, and then went to check with a mechanic to get very limited answer. Your reviews rock. Big props for the detailed info.
I enjoy almost all reviews on youtube, but yours are the most informative and useful to me. Clear and direct without an obvious bias, or if there is you say you have a like for a particular car. And your explanations of the mechanics behind the running of the cars is informative and understandable. Keep up the good work. Thanks
You are very good at explaining this. Please make more such technical videos. Between yourself and Engineering Explained, you guys have it covered 🙂
Great vid! Probably the most concise and understandable explanation I've seen in a while.
One note, related to your last comment... it's more than just how the computer is programmed. One also needs a rear differential and a center transfer mechanism that can handle more power. One car manufacturer in particular, started marketing their limited duty AWD system more aggressively into the off-road segment, and ended up having issues with burnt out rear ends from things as simple as beach travel. If the clutch packs and rear end can't handle the necessary power, bad things happen. ;-)
As an Impreza freak and proud owner of a 23G ice blue WR1 (one of only 500 released in the UK), this was a great explanation of why my beloved car can cut it in adverse conditions even with low profile, non-chunky tyres. I don't race around in it like a dick and knowing how to drive in all weathers helps a lot. I am mostly an idiot re what's under the beautiful exterior. Thanks you!
Those dashes that you drew at 1:52 - very impressive!
Best and simplest explanation of how Subaru AWD works. Great Educational vid anybody can understand
Torque split depends on the transmission, model, and year. For example, Gen 3 Outbacks have ~41/59 Front/ Rear. Gen 2s (and the Baja) were mostly 45/55. Imprezzas are all over the place.
Thanks for the video. Took me forever to find a clear, concise explanation of the Suburu AWD. Liked and subbed 😊
I like this channel. I'm studying English. I like cars. Really helpful explanation and so fun! Thank you :)
Best explanation of this system so far.
Really enjoy your channel a lot. All other automotive reviewers out there: TV, magazines, RUclips included loves to rave and kiss a$$es. You have always been very clear of your personal unbiased views. Not only that, you have demonstrated you have thorough knowledge of automotive engineering. To top that off you are a consummate presenter also. You are an excellent editor or do you do all of your videos in one shot?
I finally understand how the Subaru All Wheel Drive system works! Thanks!!
Very well explained on topic that is complex into very simple to understand language. Thanks Alex for this informative video.
I believe another advantage over other "slip 'n grip" systems is the fact Subaru's AWD has torque vectoring and can send most if not all power to just one wheel. In extreme cases should only 1 wheel have grip, it's been proven than Subaru's AWD can pull a car uphill with just one wheel, where most other AWD systems fail. Subaru doesn't mess around. It's the best and most practical AWD system out there, I feel.
Thanks for explaining. I love my Forester.
How difficult can you explain something very simple? You have done it! Congratulations!
Hey, great presentation! I've been reading about the workings of Subaru AWD off and on for years, but there are a few lingering mysteries that none of the sources address. What is it about the type of transmission that dictates the type of AWD system? Why does it makes sense, from an engineering standpoint, for manuals to get a viscous coupling while automatics get the multi-plate clutch? It seems there must be some mechanical reason, or else it would make economic sense for Subaru simply to deem one system "better" and use it universally (other than special cases like the STI). And if the MPT, under normal conditions, is sending some power rearward without locking completely, doesn't that mean the clutch plates are usually intentionally slipping a bit? How does that not quickly wear them out?
i dont know but subaru been doing it for years, way before everyone else ,they know something we dont.
Great explanation of how Subaru and works thank you .
You know, I had no idea such a pedestrian car had such a complicated drivetrain. Good info, Alex.
manual Subaru's have a center differential in conjunction with the viscous coupling. A system with only a viscous coupling would only send power to the rear when the front are spinning
Correct. the videos description of the awd system in Subaru's with a manual transmission is incorrect.
What would be interesting to know is how exactly the brake system working to stop the slippery wheels.
Alex - I am looking at two CVT SUVs. I put a lot of miles on my car for business, something like 20,000 a year at most, 15,000 a year least. I am concerned that the CVT transmissions won't last beyond 100,000 miles before needing major overhauls. I currently drive a Jeep Commander with almost 200,000 miles on it and with no issues with the German made TipTronic 5 sp automatic transmission and Jeeps QT-1 all wheel drive system. Can you shed any light on the long term reliability of these CVT units? My thanks.
Alex, can you explain how the current Hyundai and Kia awd systems work compared to others with pros and cons. I believe that the HTRAC and Dynamax aren't slip and grip systems. How do some systems work better on road or off road and how transmissions make a difference as well. CVTs and DCTs can overheat off road I understand.
Nicely summarized. Though the 2015 Outback 3.6R is now HT-CVT equipped, so should behave awfully close to the Forester XT's 60/40 setup.
That is correct. What Subaru hasn't said however is how the clutch pack is programmed. They would very easily program it to deliver a near 50/50 power split which I would say is very likely.
True, there is new "Marketing speak" for Active Torque Split Symmetrical AWD. with emphasis on the "system can send additional torque to the rear wheels either pro-actively or in response to slippage at the front wheels."
I'm guessing there are still some form of embargoes on the reviews for both Legacy Sedan and certainly for the '15 Outback.
Isn't Subaru's ABS system playing a significant role in torque distribution? I drove an Impreza for a week in icy town and road conditions and was impressed at how the brakes were quick to slow the spinning wheels, compared to my '12 Rav4 for example.
Very well explained sir, enjoyed your explanation so much.
My 2015 impreza 2.0i 5 speed manual has 50/50 awd
Forester Manuals are 50 50 split Normal driving. There is no front wheel Bias. The Manuals have a true center diff, the vicious coupling only come into play if there is slipping
I've been a Subaru driver for most of my driving life and there really is no substitute for their AWD system and winter tires. I've driven other AWD cars and as silly as this might sound. There is a reason why Subaru used the liquid to semi-solid system rather than computer controlled systems. Don't get me wrong all cars should have some sort or AWD system especially with the silly amount of HP that most cars seem to have these days.
great video, today I jacked up my 2011 outback 2.5 in the air. I shifted to D gear. but only front passenger side and rear driver side wheel spin. is that normal?
Well explained. Thanks for sharing all that knowledge
so nice explanation: handy and comprehensive. Thanks,,, Subaru is my Love
manual trans Subarus and XT models are 50/50 split
It depends on the transmission. Manual 50/50 auto 60/40
@@Dragunov302 He said Manual.
Flat4Fan what part of manual didn’t you understand
Excellent video! Cheers mate!
hahaha that username
Got a question. what are front and rear differential types? I watched a video from subaru and it says that they shift power front to back(which I get it bc you explained it here) and also side to side. With front or rear differential being open, how does subaru achieve side to side torque distribution? Maybe they are not open diffs?
around 6:15 Slip&Grip-Style System reapeats itself sthgs wrong?
Excellent description, learnt a lot. My question has a strange twist, I know the basics of AWD and am verse on 4WD, so I know the technical differences. I am looking to get a more family oriented vehicle which would be the Forester. But I want to know from a practical aspect, for light to mid offroading, say beach and camping, how would the Subaru AWD systen compare to say a Vitara with which is a 4x4 with high and low range. Thanks..
Visesh Lall In general, systems with a low range lack a true center differential (note, this is a generality since some systems still have one) which means that the front and rear differential inputs are locked together. This means that even if one axle has zero traction you can still move. In addition you would have the torque multiplication benefit of the low range for steep obstacles or more serious log/rock climbing. The Subaru system was not intended to be a rock-climbing kind of system, it is intended more for dirt, mud, gravel, sand, etc.
Ok, your explanation helped a lot. Appreciate it thanks...
Great explanation. Could you make a video explaining the Haldex AWD if you haven't already?
When the Subaru multi plate clutch locks up, does that mean it's 50/50 front/rear? Can it send more than 50% to the rear?
Why does the TFL up hill on snow show the Subaru failing when the steering wheel turned? and the CX-5 passing the test?
Thanks Alex it was awesome explanation,
Can you please review and explain the quattro system of an Audi RS3? It is different from the one in an A3.
I'm confused, from what I know the the CVT models have viscous center joint with no Differential and Manual has Third differential and locking clutch pack.
Could you please do a review of the AWD systems in CRX/RAV4/Rougue just for comparison sake?
Thanks.
can you compare the subaru awd system with acura sh awd?
sam henderson Tricky one. The Subaru system always sends some power to the rear axle, usually it is about 40%. The Acura system will normally default to more of a front bias unless slip happens or you push the car harder. Pushing the SH-AWD system harder it is possible to send 90% of the power to the rear without slip. The Subaru system (2015+, most models) can only split power 50/50 unless there is slip, so there's a sort of rear bias under power in the Acura system. Also Acura employs a torque vectoring rear axle which can send power left and right with or without slip, this is much more capable in terms of handling than an open differential like you find in the Subaru. They are very different systems with different missions. The Subaru system is less expensive but very capable and has a good feel in snow. The Acura system was designed to improve the driving dynamics of their vehicles to make them feel more like RWD drivetrains.
No because Acuras are FWD and cant do a 50 50 split w/o a locking dif. thats why Subarus have a locking dif in Outback and foresters. WRX Sti are still 50x50 and is the Crossteck, the cars that dont have the lock are 60x40. But the models with out the locking diff will resort to 50x50 upon demand as with the Outback and Foresters with out the locking diff.
Thanks for the lucid video. I wonder if you can help. I am trying to
diagnose a ticking sound coming from the bellhousing area of the drive
train on my 97 Subaru Outback. When running at high speed, the tick in
inaudible, except on deceleration. The sound is most pronounced at idle.
Listening from underneath, the sound appears to come from the
bellhousing area.(The car is AT) From the area of the flywheel that is
visible, the flywheel appears to be burnished in comparison to that of
my other 97. I thought that maybe a stone or something found its way
into the bellhousing because there is no cover for that space. (If the
stone were trapped, centrifugal force would keep it stationary at high
speed.)
I made a chalk mark on the balancer and manually rotated the crank. A
pronounced clink occurs at the same spot with each rotation. I had a
friend rotate the crankshaft while I lay underneath. The sound came from
the transfer case area on the driver side. When the crank came 360
degrees from my mark, I got the same sharp click, like a drop. At 180 to
my mark, there was always another barely audible click. (like something
re-setting at 180 and dropping at 0/360.
I should mention that the car drives well with no signs of diminished
function in any area.
Are all the torque converter bolts tight? Otherwise it could be many issues, bad torque converter, something wrong on the input shaft of transaxle, whatever. I'd check bolt and then have a transmission shop familiar with Subaru look at it.
Lake Nokomis CV joint
I have that same sound coming from the left front. Busted CV joint.
Well done Alex.
This was a great video!
I have a 2011 impreza 2.5i wagon auto for my work car. I live in the mountains and get alot of snow on our interstates before they plow. I bought it used right at the end of last winter and only got to drive in snow once. if i remember right it wanted to fish tail. is that because of my torque split? or could it be bad tires or the light weight of the wagon in back?
Wow! Great explanation; very easy to understand. I've always wondered how Subaru's system differed and now I know.
Just one quick question: how much maximum torque can the Active Torque Split system send to the rear wheels?
assuming that isn't just applying breaks to the contrary wheel :P
Because of the design it depends on what wheels have traction. If all four wheels have traction, then the maximum would be 50/50. If however one of the front wheels had zero traction, the system could send nearly all the power to the rear (90%+) until the front wheel(s) regained traction.
Alex on Autos Thanks, Alex. How about side to side? Without a rear differential, how would torque be transmitted to either side?
***** The system uses an open differential front and rear so the power split is around 50/50 unless slip occurs. If slip does occur then the brake-based traction control system would step in to slow the spinning wheel down. Torque would still be around 50/50 because the brake system does not "stop" the spinning wheel, it attempts to slow it down to spin at the same rate as the other wheel therefore keeping the power in balance.
Alex on Autos Cool beans; thanks for the response and great video.
Nice video Alex
I have had a Subaru forester 1997 (automatic) from new (approx. 70,000 miles on the clock), that has been great for all the years with very little to do other than annual services. However, recently I have had a lot of vibration & shuddering on the wheels when making slow tight turns (left or right) but never on the straight. It is difficult to identify which wheels the noise or shudder comes from and I don't feel much through the steering wheel. I have had all differentials replace that has reduced the frequency but not eliminated the problem. We hope it isn't the automatic gear box but has anyone got any ideas what to do next.
18 feb 2019 7:48 am est:
'(1)Low Power Steering Fluid: 1 of the most commonly seen reasons for a shudder during
turning is low power steering fluid. If the fluid level is low, the power
steering rack and pump don’t have the right pressure to operate. It could also
indicate a leak somewhere in the power steering system, which will need to be
inspected.
(2)Failing Power Steering Pump: If your power steering pump is beginning to die,
it could very easily cause these symptoms. As the pump fails, it produces less
and less pressure for the power steering system, causing vibrations, shudders,
whining noises and more.
(3)Kinked/Blocked Power Steering Line: You need clear power steering fluid lines to
ensure the right fluid and pressure distribution. If a line has become blocked or
kinked, or is leaking, it can reduce fluid pressure and flow.
(4)Failing Wheel Bearing: While its most common to experience a roaring noise when a
wheel bearing is beginning to fail, they can also cause vibrations that some drivers
interpret as a “shudder”.
(5)Failing Differential: If you have an all-wheel drive vehicle, it may be a problem
with the front or center differential. When these begin to fail, they will create a
shudder, particularly under the stress and strain of a turn.'
in www.yourmechanic.com/services/car-shudders-when-turning-inspection
from google(tire vibration during turning)result 2
@@arnon-jaya Thanks for this very thorough reply and has given me something to think about and try out. I will keep you informed........George
HI Alex.. great video. i have question. I have 2014 Forester, installed 235/60 R17 yet the spare wheel is the original factory wheel which is smaller in diameter, if I install it, well the AWD light flashes? if so, will it damages the transmission?? I saw some video people install a fuse in an empty slot in the fuse and the FWD light comes on, I tried all empty fuse slots, the FWD light never came on.
appreciate your kind advise.
Ok so I have a 5 speed 09 outback xt. I watched the guy from Engineering Explained go through all the subaru awd systems and I could understand why the ones for the sti and wrx were designed the way that they were, but I don't understand why the manual and automatic here are different? Is there a reason why the manual transmission subarus Need to have the viscous coupling setup vs what they have in the auto or is it just something that subaru did randomly? Is it because they think less people buy the manual versions anymore /or they don't make them entirely and so they see no need to update the mechanics in those models?
The picture at 1.24 is incorrect. 1st the engine is very low and wide and the drawing is spot on but it should be rotated 90 degrees. 2nd the gearbox is pretty long and starts where the windscreen is and goes all the way to the backside of the front seats, which means that the actual driveshaft at the back is pretty small -) Next time provide the pics of the car and gearbox! Another thing to mention is that the TZ gearbox provide 90% to the front and 10% to the rear as a normal drive and able to shift to 60/40 if needed, also in the manual mode (1st gear) they can operate at 50/50...
subscribed! very knowledgeable!
Thanks for the video. Nice one. I am looking to buy the Forester. Can you say how much difference in 2.5 & 2XT options?
Excellent - very clear.
Loved the video!! Any chance of a Levorg review??
I have an 03 Forester, at a complete stop on slippery snow road, when I accelerate the front tire spins in the snow then about 1 sec of spinning the awd engages, is that normal?
U should have explained how it transfers torque from front left to front right!does it have a EBD using open diffs and ABS or has it got some diff locks but overall the movie is good!
It depends on the model. In general Subaru uses open diffs and the ABS controller to direct power from side to side.
Hi, I have a couple of questions. Is the multi plate transfer clutches in a oil bath or something?! What is preventing wear and tear of the clutches? Can they overheat and if yes, is there usually some sensors for that?
I read elsewhere that the CVT in the 2015 Outback (and others) is not designed for engine braking. Downshifting with the paddles will increase wear and tear on the CVT. Is this true?
If you are for example spinning on ice and suddenly "catch" some tarmac, what is preventing the shock from destroying the CVT cones due to slippage?
I recently tried a Outback 2015 - the electronics limits the RPM to prevent strain to the CVT (as I understand it). I am unable to climb steep hills and even a simple diagnoal test (uphill) caused the outback to simply not move at all. I wonder how weak/strong is the outback in case of towing a trailer uphill (especially when starting). I supposed you can't add much weight when the car is incapable of moving itself without load. I live in Norway so the only Subaru I would consider buying is the Outback 2015 2.0 diesel. More details on this is appreciated :) (thanks for a nice principles of operatoin explanation).
Svein Engelsgjerd Yes they are a wet clutch design. In theory any wet clutch like this can overheat, Subaru helps prevent this by using more plates to reduce the load and improved cooling. The CVT doesn't have any durability issues when downshifting per se, no more than in normal operation. Slip is unlikely in those situations because of the belt design, but as you noticed the low end ratio is not very low and that is the limiting factor on steep grades or towing.
+Alex on Autos
Hi and thanks for answering. I do have a few follow up questions if you don't mind. 1. Wet clutch design: Does this particular design rely entirely on the viscous effect or is there actual friction involved between the plates? 2. Slip of the CVT belt. Is not the belt design exactly the reason it can sllip? If a belt is on two smooth surfaces - is it not likely that the belt may slip if the car suddenly snag in the tarmac?. I realize of course that the energy would have to go from the tires, through the rims , through the differentials and so on before it ends up in the gearbox (which does have the converter (with clutch?) that also dampen the shock a bit). Regardless I am concerned about this.
Svein Engelsgjerd There is friction between the clutch surfaces, this is not a viscous coupling like in the Subaru manual transmission. The belt is a steel belt design that is not exactly smooth per se, but by its very design it really doesn't slip like tat, any like forces would probably get absorbed by the torque converter.
Regarding the clutch pack again: On Subaru's website the outback is claimed to have a 60/40% split between the forces. Would not this mean that the clutches are "mostly engaged" ?! I am sure it works, but logically it sounds like they are prone to wear and tear - especially if used often. On the other hand normal dry clutches is (very) hard to wear out unless they get hot. Is there a heat sensor/monitor/estimator for new outbacks so you know when to relax/wait a little?
Svein Engelsgjerd There is wear involved as with any clutch but it should be very long term. There is a temperature sensor but it is the transmission's sesnor since the AWD and transmission are both inside the same case.
question ....if my subaru forester (sf5 1998) is missing one front right drive shaft will it move? for how long will there be damage??
How does Subaru send all the power to one wheel if it has a traditional rear end? I thought I've seen a video showing a Subaru on rollers where one wheel had traction and it climbed up.
+boostedmaniac Traction Control. If they sense a wheel slipping, they'll lock the brakes on that 1 wheel. If you watch the one-wheel traction videos closely, you'll see loose wheels jerk and stop when the car pumps the brakes to get traction.
I'm confused...
1. I thought the transfer case is what separated AWD from 4WD.
2. Do both Subaru's automatics and manuals use the same power distribution method?
3. If power distribution is almost always 50/50, doesn't that cause problems when turning?
Peter Schmidt 1. Once upon a time it was, but now the waters are very murky. 2. No, they are different. Most CVTs use a multi-plate clutch and most manuals use a viscous coupling. 3. The viscous coupling allows power to flow approximately 50/50 without actually having them bound together which allows you to turn without binding.
The Mountain Garden Ah ok, thanks for the info.
In our 2013 Outback 3.6R (traditional tranny) I've been under the impression that the split is rear-wheel-biased 45/55 (front to rear). Is this referred to as Variable Torque Distribution on my particular model year? Am I correct or did I miss something while doing research? By the way, great explanation on the AWD system.
The following is copied from SOA website:
Variable torque distribution AWD:
An AWD system designed exclusively for 5-speed automatic transmission, E-5AT (with manual mode) models to provide aggressive, sporty driving with increased turning abilities all while retaining the fundamental driving stability offered by the Symmetrical AWD. An uneven 45:55 front and rear torque distribution has been set for the front and rear tyres. Sending greater torque to the rear wheels can reduce understeer, a trait that plagues 4WD vehicles, when cornering for smooth and agile handling. Torque distribution is controlled automatically up to an equal 50:50 front and rear to suit road surface conditions for both sporty driving and stability.
Because you have a 2013 model, you are correct. Subaru made a change to the 3.6 L drivetrain in the latest generation. The current model with the 3.6 L engine does not use the Torsen centre differential any more.
Alex on Autos Thanks Alex, I've owned my 13 OB for almost 3 years and have found the AWD system (very effective) but very confusing. You've definitely cleared it up for me. Thanks again.
The CVT 3.6r have locking diffs. for starting 50x50. If you are in motion and your in snow, or climbing, in mud, rocks, the CVT will split 50x50 and send power to the wheels with the most grip... FWD cars cant do this. Jeep, and Tacoma owners spend thousands to get the same grip Subarus get.
Sorry, didn't get it, speaking about Subaru Outback 2015 model year (new gen) what system 2.5 has, what 3.6 has, are they different? Are they 60/40? Is for Forester the same?
What is better viscous coupling or multi plate clutch and why?
Thank you for the video!
They are different, not better really. The 2015 models with both engines and teh CVT use the multi plate clutch and a 60/40 bias, manuals use the viscous coupling and a 50/50 split.
Alex on Autos Thank you for your response!
What about CVT, as I understood from Subarus materials - Outback 2015 has latest generation of CVT and 3.6R model has more heavy-duty version. Is it really new? Maybe you know what did they improve?
Jack Tomson
There were only minor changes to the CVT for the 3.6R model and the changes were mainly to help it handle the increased power output from the larger engine.
You're telling me the manual transmission subaru never has a 100% direct connection to the rear wheels? If so... that explains a hell of a lot of why the car feels "dead" and "souless" compared to other MT car's I've driven. I was wondering wtf was up.
How is it that the clutch packs of other manufacturers (like Nissan) tend to overheat even though they are rarely engaged yet Subaru's never seem to overheat even when flogged, and is always engaged?
It is all in the design. By putting the clutch pack into the transmission case it can take advantage of the transmission's active cooling system. When clutch packs are on their own they don't have a radiator to help dissipate the heat.
04-05 STi splits 35%front 65%rear 👍
are the late 2000 outback and forester models engines like this? centered?
Great Video. But I own an 2014 Forester with the cvt. So let's say I'm in a slippery condition. You're saying that my car would have 60/40 split instead of 50/50 ?
I am confused.
In my 2013 forester manual 5 speed the AWD system works like the 4WD system on my truck... power to the front left tire and rear right tire.. difference being 4WD has locked hubs with a LSD or a locker in the diff.. AWD having open diffs using the same setup but computers monitor wheel slip, if slip is detected it then redirects power to the opposing wheel through a clutch pact. I have performed many tests on ice and proved that is how my system works.. the power split on my Subaru is 41-59 and if needed it will do 50-50.. I have never experienced a situation where my power split was 60-40.. the front tires usually do not slip first except if the front tires have no traction but rear tires do..It is always the rear tires that slip first for instance on a frozen lake or a sheet of ice at a intersection the majority of the power goes to the rear and the rear kicks out until the front wheels have caught up in wheel speed. While I am cornering I apply more power and the rear kicks.. If what you are saying is true about 60-40 split then i should experience under steer or feel the front slip during hard acceleration right? Am I misunderstanding something? How I have felt the car drive and what you are explaining do not match. Did Subaru change their design between 2013-2014? Even a certified Subaru mechanic has explained to me that my forester has a rear bias and if needed can even the power between the front and rear but never front wheel bias. Now other vehicles i have driven that have a setup such as the CRV I for sure felt under steer while cornering and front wheel slip during hard accel... which would make sense that the CRV has a 60-40 split. But I have never felt under steer in a Subaru cause of a front power bias, if under steer happened it was the drivers performance.. I bought Subaru over Audi, BMW, Honda, Acura and all the other companies selling AWD because I was told the Subaru AWD was not a front bias setup. Last thing I might add is I have a controller that allows me to manually choose power between front and rear.. like what you find in the WRX STI.. I can never do a 60-40 split. It is always between the range of 50-50/21-79. But even on my buddies Forester without the controller he still has a rear wheel bias.
I appreciate the video, I would love to hear back from you with your thoughts.
+duuane cooper Subaru is always updating their systems. What was the norm in 2013, they completely change by 2016. They offered low range gears well into the 2000s Foresters and Outbacks in some markets. Granted it wasnt terribly LOW for a low range, but it was better than regular hi range gears. V
+Y10Q thank you for the reply . I simply love what Subaru does. I'll be coming to your channel later if I have some questions about newer models. Thanks!
Does this info still hold true with the new auto with CVT(continuously variable transmission)??
Thanks
Great video btw!
So in a 2005 WRX it has the viscous transfer case behind the transmission, but you said they program it to be 50/50 by default? I wanted them to do that AWD test on an "older" manual transmission car but I just can't find it.
Well with a viscous coupling there is no programming per se. The coupling has two sets of plates that alternate ABABABABAB. The As are the input the Bs are the output. Assuming that the front and rear are spinning the same rate, the power flowing through the coupling can be 20-50% or so depending on the exact design. If however they start spinning different rates, the fluid becomes more viscous and the coupling "connects" more aggressively. There will always be some slip, but a 90%+ transfer is fairly common.
On a side note, do you know how Mitsubishi does their AWD system? All I can gather from what I am able to find is that all their differentials are electronically controlled by a computer that senses what tires need the grip, nothing specifically mechanical.
Jeremiah Yareff
If you are referring to the Lancer EVO, then early versions uses a viscous coupling but since about 2001 they have been using an electronically controlled multi-plate clutch pack that not only reacts to wheel slip but allows the computer to deliberately allocate power to the rear at various levels.
Thanks for the reply. Very quickly too. So with that system (all it has is ABS I think, and just the drive train) is there any control to left or right wheels, or is that purely the differential (needing to be partial locking to do left to right)?
Alex on Autos
2010 EVO specifically I guess. But yeah, that answers the question.
Subaru sends 60 x 40 since 2016, to increase fuel economy. Prior models are 50 x 50 like my 2012 Outback 3.6R and its how you get the best traction. Technically Subaru's are Rear Wheel drive up to 2016 or 2017 where they split 60x40. What makes a FWD is the Transverse engine either, 4, 5, 6, 8 cylinder engines... Subaru does not have a FWD engine but a flat 4 or flat six similar to a v4 or v6 that can produce more torque with the power it has. People should stop comparing Subaru's to FWD cars they are not the same at all...
hello i have a 2007 forester 2.5 non turbo automatic, the locking solenoid seems to have all the wheels locked, i have a grabbing feeling and rubbing sound when making turns, no transmission or abs codes, any advise would be greatly appreciated
I'm not expert on these but worked on cars many years. Are you saying that without any lock button engaged, the solenoid appears to stay on to lock system and you get that abnormal sound? Appears if you are using the lock button you need to turn it off, as its only designed for use in extreme slick conditions like if you're getting stuck or something. If its turned off, have a shop look at it as if its engaged on its own, you will wear out drivetrain / tires or both, as the back tires are supposed to turn less around turns than front due to the arc of the turn, and forcing them to turn same rotation binds up drivetrain.
Ok, this must be an older video. So what will the 2018 Subaru Ascent have in it. Thank you. Roger
My Subaru outback is a 15 and my all wheel drive is messed up and it only front wheel drive now what is wrong you think
What about the transfer of power from left to right on both front and rear axles?
EGGINFOOLS The Subaru system (most models) uses open differentials front and rear, so there is no ability to do that beyond the brake-based traction control.
Alex on Autos i see. Thanks
Hi Alex, just out of curiosity, which AWD system is the best for winter driving between Subaru's, Acura's SH-AWD and Audi's Quattro? Would it be reasonable to say that they are about the same?
For winter driving Quattro or Subaru would be the better choices because both systems send nearly 50% of the power to both axles (longitudinal Quattro only) while Acura's system is 90% front when starting unless there is slip or you're driving the system hard. This results in the Subaru and Audi delivering a more sure footed feel from a stop.
People have hooked up data loggers to Subaru's ECU and have found that the clutch fully locks under acceleration from a dead stop and slowly unlocks as speed rises unless other conditions command more locking. It also showed that clutch lock up in response to slippage is more aggressive the slower you are going.
Are you sure that 60% front/40% rear applies to manual transmissions? I know my 01 Outback manual is 50/50 in all conditions.
That said, there is one downside to having the transfer case built into the transmission: If you experience binding in the transfer case, you can't simply replace that part. You have to replace the entire transmission. I've gone through two because of failing transfer cases. (I know I should have sold the car after the second one died but for reasons I can't get into here I can't simply get rid of it).
you need to see the video again. he told that the manual transmision goes 50/50
That binding you talk about is the centre diff assy, it can be replaced.
Alex on Autos I haven't seen a 2015 Outback review from you. Can I assume it's not on the schedule?
We are still working on this, stay tuned :-)
Thanks and please review the 3.6R. I need more power...
I am building a dune buggy with a 2000 2.5 non turbo Subaru standard transmission. How can I transfer all power to the front wheels.
I would keep both inner and outer joints of the front axles (can't operate without either), without the actual shaft between them.
I currently have a bad driveline in my 05 outback manual transmission I'm wondering if I can run it without the rear drive line maybe half of the driveline can anybody out there tell me if it will work or if I will hurt them clutches
hi Alex, if you have to choose between a Subaru flat 6 and turbo 4, which one would you pick and why?
I have never cared that much for the 6. The power output isn't much better than Subaru's turbo 4, it's honestly not much smoother but it does add a decent amount of weight to the car. Personally I think I'd get the naturally aspirated 2.5L engine however. It's going to be the lower cost to operate, maintain and repair in the long run.
1+ on the naturally aspirated 2.2L or 2.5L after 2009. Don't consider the turbos if you're in cold weather. Way more maintenance. and I think 2002's-2008/2009 the outside headgasket will leak like clockwork somewhere between 110k-70k miles. Even when you put a new one on, unless you use the fancy multi-layer steel gaskets which I guess for the cost difference, no one uses.
Usually you'll get lucky and the gasket won't leak on the inside of the engine which is better though.
Thanks Alex!
Doesn't the current WRX have a rear wheels bias (more power to the rears) compared to this car you're reviewing?
The WRX uses a different style "transfer case" inside the transmission housing. The power split for 2015 is 41% front and 59% rear and this is combined with a limited-slip helical front and Torsen rear differential. The whole package is quite a step above the standard Subaru system.
Thanks for the info, Alex. I hope you get to put a WRX through its paces in a review soon!
Alex, you're saying "power" when I think you mean "torque." Perhaps define those two terms upfront and use an example that the torque any wheel can receive cannot exceed what traction it has, and that power = torque x speed. I think also the location of key components is not relevant to the theory of operation, despite Subaru's marketing. Best to define the terms, define the typical components, discuss the theory of operation using those components in the various models, then describe where components are located in Subaru's implementation. Thanks for your efforts!
So is my 2013 Legacy 3.6 R a Muti plate unit vs vicious?
Neither, it is a Torsen style true differential
+Alex on Autos ahh got it Thank you !
+cobra454tim they use Torsen on Tribecas and Outbacks, drawback is that when it breaks, you gotta stop and fix it. It is a mechanical system. You can't drive it. When a viscous system breaks down, it acts as an open differential and you can drive it like that forever or till you notice that you have an open diff
Since you seem to know your stuff do you know what system the 2015 Legacy 3.6R has?
The new Legacy uses the same AWD system on the 2.5 and 3.6 models (in 2014 they used different systems). It uses a multi-plate clutch pack to distribute power front/rear. Under normal conditions power is 60/40 F/R.
Alex on Autos Awesome thank you for that information. Very informative posts which are greatly appreciated. Correct me if I am wrong but that means the Legacy is capable of transferring 100% of power to front or rear if needed and left and right..?
Kamber Bulica Well it depends on how you look at it. If no wheel slips, then the system will vary from 60% front to 50% front and each tire will get 25%. The system is not capable of sending more than 50% to the rear or more than an equal share side to side unless there is slip. IF a front wheel slips, the system can send 100% of the power to the rear and if a rear wheel slips 100% can go to the front. No version has torque vectoring in a mechanical sense so power is essentially equal across the front and rear axle (L to R).
Alex on Autos Awesome ok thank you for all that information. For sure saves me a lot of time.
If I have a 1996 Legacy (A/T) with AWD, what system do I have and what is the bias?
What is your gearbox model?
How do you find that out?
Look at the VIN plate under the bonnet.
I know my particular model has a 4EAT model transmission.
Yes they all have 4EAT for about 25 years now, apart from the 5 speed ones. It must have a number starting TZ or TV on the vin plane.
I have a 2014 Forester, and I must say that after having a 2001 CR-V SE 4WD for almost 12 years and selling that for the Forester last year, the Forester is a lot better with its Symmetrical AWD system. About power distribution, certain Subarus, such as Tribeca, WRX, and WRX STi, send power about 40% to the front and 60% to the rear.
This video is limited really to the 2015 product line excluding the WRX and WRX STi. (The Tribeca is gone). The WRX uses a different style "transfer case" inside the transmission housing. The power split for 2015 is 41% front and 59% rear and this is combined with a limited-slip helical front and Torsen rear differential. The whole package is quite a step above the standard Subaru system.
How to engage 4WD in 2002 subaru forester x20 automatic
I don't think the 'steady-state' 60:40 distribution of torque is correct in the CVT models. I also think you give too much credit for the prowess of the Subaru AWD system currently sold. Their system *is* better but mostly due to better control modules than anything else.
I believe the torque distribution is more like 90:10, but continuously variable, so up to 50% can be sent to the rear. Unfortunately, I don't think Subaru is officially sharing this info with us.
Also, your description of slip-and-grip systems is somewhat outdated as many manufacturers have move also to a continuously variable distribution. For example, the new CX-5 and RAV-4 are dynamically changing torque distribution as well.
You are right that the Cherokee, when properly equipped, has a superior AWD system. Subaru's system is much more similar to the RAV-4, CR-V and CX-5 than to the Cherokee.
I questioned the numbers and Subaru confirmed that much like Torsen center differential vehicles the current CVT system sends 40% of the power to the rear most of the time. This is actually apparent in icy conditions as there is no reaction time in this system. Compared to the CX-5 there is a big difference where there is noticeable front wheel slip prior to engagement. The RAV-4 in its current generation is a 100% font under most circumstances system although you can command the clutch to lock up under 25 MPH by pressing the lock button.
Alex on Autos Torque split varies on subaru models but I think the main trick of the Subaru MPT AWD system is smart programming. I would be hard pressed the find the source but I recall reading about it and here is what I recall. Subaru advertises their system as proactive and it's true. It is mostly but the programming differs on various models of cars however some basic ideas of it's 'proactive opration' are: When the car is starting to move from 0 to up to speed the MPT is locked for 50/50 split. So you always start with full lock as you pick up speed the system progressively decreases the MPT pressure where around 40km/h or it's mostly FWD. If you start pressing the throttle the system will immediately start locking to whatever ratio is determined by the ECU but the main point is that it doesn't wait for slip it reacts to your throttle and progressively locks up the MPT as the ECU programming dictates. The system will also react to wheel slip of course if it determines the axles are spinning at different speeds it will lock up the MPT and that difference is very very small so the MPT locks up quick to transfer torque to the opposite axle and to prevent wear on the MPT. Under no condition does subaru system allow a large speed different between axles because if such an event were to occur it would likely destroy the MPT system so if the ECU detects large different between axles it will actually disengage the MPT completely throw an FWD warning light on the dash and obviously not engage the system until a reset.
This is the system present on my 05 4EAT legacy and probably most other basic 4EAT cars. I know WRX and STi use a different system with planetary gear sets in the center diff and all kind of other fanciness to give them varying static split ratios that the driver can control. But even the basic system Subaru has created is excellent especially when paired with an LSD in the back and/or front. It really is great. You have AWD when you needed and none when you dont.
sigsegv0x0b
This has changed for the CVT Subarus according to Subaru. The CVT equipped models do not have the clutch pack at full lock from a start in current models, it is a partial engagement allowing for about 40% power transfer to the rear. They also claim that at higher speeds the current models maintain this split rather than biasing to the front.
Alex on Autos
Thanks Alex for the update!
If the split is 60 front 40 rear on steady-state highway driving and if they use wet mult-clutch plate, how does the fluid not get really hot from the energy lost to friction and how do they maintain good fuel economy in the process (I really don't know, not a trick question)?
David Lee
That is an excellent question, and one to which I have never received a satisfactory answer to. There is always energy lost to friction of course, but that also happens in viscous couplings. It is my understanding that the fluid used has properties that lie between traditional clutch pack lubrication and a viscous coupling. This allows some shear forces to transfer from plate to plate even if they are not fully coupled, then of course it can still lock completely. There are a few other vehicles that use a similar "friction additive" like the Jeep VariLock couplings of yester year. In general these just rely on convection cooling, which appears to be OK but I have always thought that some form of external cooler would be required.