You did a great job describing it! I was an engineer on the development team for this system, the pistons to compress the clutches are actually in the outside cases and the holes in the clutch hub and basket are to drain oil out of the clutch packs. Another thing to note is the RDU is over driven from the front to allow torque vectoring even when there is no difference in wheel speeds front and rear. Great video!
Awesome! So that means the rear wheels are rotating freely until there is a demand for torque on the wheel? Can you give us a hint about the life expectancy of this system?
do the clutches fail into a locked state, or an unlocked state? If just one failed, could the control figure that out and keep the other one locked whichever direction you turned?
Great job breaking down SHAWD with no pretense, really well explained I learned how complicated the controls system needs to be to activate the individual clutch packs. Great job, you are a smart dude.
This is cool. I recall looking up Honda's patent filings to figure out how it actually works, back when SH-AWD came out. Now I get to see the internals.
Oh, this is way simpler than what was in the patent. The patented system has geared shafts driven by each side at 102% of their speed. Applying clutches between an axle and the shaft spinning slightly faster than the other axle allows transfer of torque with minimal loss of power.
Your presentations are spot on! You cover all relevant topics with clear understanding, but avoid wasting time. Keep on same track, cause you're nailing it. A top channel!
One thing to note is that the RDX SH-AWD system is a simplified version of the system found in the 2nd gen RL. The system in the RL can overdrive the rear wheels upto 5.7% faster than the front wheels while the RDX overdrives the rear wheels at a constant 1.7%. The RL system also incorporates a planetary gear set within the clutch packs that allows for the accerlation of the rear wheels. Really clever system.
Fantastic video. If you’re worried about Phillips screwdrivers stripping screws, try a JIS (Japanese industrial standard) screwdriver. They don’t cam out and have better engagement!
Excellent point. Phillips and Pozidrive (Europe) seem somewhat interchangeable, but Phillips and JIS are absolutely not compatible. So many of us grew up thinking Phillips was shit because we stripped a bunch of screws when taking apart Japanese electronics. At the time, none of us knew the screws were JIS, and we were stripping them because we were using the wrong tool.
Old tractors have rear brakes only, with separate left and right brake pedals. You step on one or the other when you need torque vectoring, usually to make a really tight turn, or keep a slipping drive wheel from digging in deeper.
@@speedkar99 an open differential delivers equal torque to both axles, regardless of rotational velocity. Braking on one side directs more torque (and thus more power) to the unbraked side. On the braked side, some power gets converted to heat. Subjective experience tells me it works quite well.
Mr Speedkar is a master of automotive technology. As for me, my first car, in 1959, was a 1929 Model A sedan. I like to imagine the ghost of Henry Ford viewing, with some. consternation, the complexity of modern automobiles. I think he might wonder at how the manufacturers can produce such sophisticated products at a price that car buyers can afford. And rightly so.
Have a 2011 RDX with the SH-AWD since new and it is still a blast to drive on windy backroads. The only real issue Ive had with the car is the waste gate actuator and the sun baking anything that's not painted metal on the outside. It is a great car still
Very informative- I had no idea these were basically locked diffs with clutch packs that allow it to turn. Getting on the throttle on SH-AWD mid corner is actually pretty fun.
Instead of the Dual Pump Fluid that Honda mandates, I put Mobil1 Synthetic ATF Multi Vehicle (Silver bottle/black label) in the rear diff of a 2019 MDX. As per 540RAT engineering blog, it’s tested as having the strongest mechanical wear protection, even better than Amsoil. I also use it in the ZF transmission. This was 7mos ago. Working just as it should. Thanks for this video!
@@gogozy1 yes when this mindless thin stuff started taking over. It wasn’t cutting it. I also don’t believe ANY OEM fluid is good at protecting. It’s only good for lining those company pockets. 540RAT tested a bunch of the thin new gen stuff like Mercon LV, Maxlife (my old fav), Mobil Synthetic Multi Vehicle (blue bottle, not Mobil1), Castrol Transmax and they all failed with “0 psi.”
as an engineer nothing keeps me up nights like people ignoring my usage recommendations... some brands might want their product to self-destruct confident that you'll buy another (MB, BMW these days?) but I think Honda and Toyota want their good engineering to be their calling card.
@@lqr824 true but even Honda and now Toyota have gone the route of turbocharging. Maybe they have something up their sleeve but I don’t see them lasting like the current 2GR, 3UR 2UZ did..
Great video, I love these mechanical breakdowns. I hear a lot of reviewers claim the Honda iVTM-4 is the same mechanically as the SH-AWD except the software won't do the vectoring. Would be interesting if you got a hold of the iVTM-4 to compare.
I have an AWD MDX and it makes that bigger thing much easier and fun to drive - also makes me wonder why they didnt make an AWD Integra sku. Could have been awesome - especially if they added some level of manual torque assigning, could keep it vectoring, go 50/50, 30/70 or something lol (idk if thats even really possible) but even just SH AWD would have really made the new Integra a lot more compelling, especially since Acuras is great in my experience. Could have competed as a higher end GR Corolla or something.
Unfortunately it would make the cost of the car leave the demographic they're aiming to serve. That, and the R/D of adding AWD to the new integra would defeat the purpose of the TLX. I dont think they want to invest in designing a new transmission auto or not for the civics drive train when they sell the TLX anyway. Manual SH-AWD hasn't existed since 2014 and I think this is the reason behind it.
The recent SH AWD system has been simplified. I think the older generation has planetary gear sets in the unit to either drive the rear wheel at 100% or overdrive (+3 or 5%? forgot the exact number). Now it seems it is just single speed (overdrive) controlled by two clutch packs.
Correct. The 2nd gen RL had the most advanced SH-AWD implementation using the planetary gear set within the clutch pack that allowed for up to 5.7% overdrive.
I think the hydraulic pressure applies force from a piston in the end castings to squeeze the clutch pack. Those holes you pointed out are for lubricating the clutch faces.
Very interesting to watch. My 2013 Mitsubishi Evolution X has a similar rear differential. It’s an open rear diff with what Mitsubishi calls “active yaw control system.” Torque vectoring pretty much for the rear wheels with an active center differential. It can send 100% of power to an individual real wheel during hard cornering. Great for the race track.
Rear unit of Evo is actually quite different. Both wheels are powered mechanically via differential (which is missing here), so even if clutches are open - it's still awd car while this one is FWD then. In Evo, power goes through gearing, not just the clutches. Evo also cannot power just one rear wheel.
This is a really cool video! Thanks for sharing! A few questions: 1. Does the transfer case use a variable pressure-controlled clutch as well to dynamically distribute torque between the front and rear wheels as well? If so, what mechanism does it use to vary the transfer case clutch pressure? 2. How does the rear differential measure wheel torque eg: 25% left and 45% right? Does it just use oil pressure only? 3. How long do these clutch packs last? Can they be replaced without replacing the whole unit?
This is amazing. Never did I think I would see a manufacture outside England take one of the most reliable parts of a car and turn it into an overly complex mechanism that surely will be a high failure point. And will never make it to 200K+ mileage with minimum maintanance like a regular diff with a limited slip inside it.
Thanks for the video. It was like I was right there with you. I have a couple of questions: 1) how did you get your hands on that part (the rear diff)? I heard you say it was off an RDX, but was it a wrecked vehicle? so, history and where you got it from. 2) judging from your disassembly, some of those parts cannot be reused. Was it solely for the sake of a video? Or is that part of a car that's being disassembled/rebuilt? I really appreciate how professional and straightforward you are in this video. Being a gear-head myself and a former tech no longer working in the industry, I still maintain a very strong interest, especially with Honda/Acura. Anyways, this was an inspiring video and I appreciate what you do.
Glad your brother donates so many clothes for your clean up. Very interesting video. Since you do so many automotive investigations, is there a best brand, better design, better longevity, auto that you have found.
I bought a base Prelude (5th gen) because I had heard reports of SH breaking. I installed a bullet-proof Quaife differential instead. The warranty specifically mentioned that racing wouldn't void it.
10:48 thermal pad, for heat dissipation as well as transferring heat to case 11:11 inductor probably is part of voltage boost circuit to drive the high(er) voltage Brushless DC motor (BLDC) for better speed and torque control.
Indeed the term used is strange. Actually, it came from the heritage that it's a revised version of its ancestor brushed DC motor. Brushed motor, although the power feed is DC, but it's internal commutator (brush) contacts change the current direction flow through the coils. Brushless version is doing a similar thing by - change outside stator from permanent magnets to coils, - change the inside rotor from coils to permanent magnets - since there is no commutator by rotation to help changing current direction, so electronic circuit is used. The DC power feed go through 3 sets of simple switching transistors (just ON and OFF, including reversing the current flow direction) to drive the stationary coils . The waveform is very simple, e.g., first phase: POSITIVE 0-120 degree, NEGATIVE 180-300 degree. The other two phases do the same with 120 degree phase offset. P.S. a similar type of design with much refined waveform can AC Synchronous PMSM motor, typically used in EV drive motor. The waveform will be just 3 AC sinusoidal waveforms with 120 degree offset.
3 phase offers better power continuity than 2-phase motor. Nicolas Tesla's original AC power generator is a 3-phase system and the motor is also 3-phase.
Interesting, I wish you got the Lexus TVD too, its an open diff with individual brushless motors for each side and it's used only in 2 performance F cars - RC F and GS F, the GS F always had TVD while RC F Track Editions do not have TVD and since 2023 they also stopped making TVD for RC F. It has a separate ECU system for itself as well.
Front differential is typical for a front wheel drive transaxle. There's a transfer case that outputs power to the rear axle directly from the front differential.
@@4x4.tests.on.rollers concur with the objective .... should of been more specific as to relate with componentry (electric oil pump and clutches ) although Honda has a more reliable system. I've just replace my oilpump two months ago😮💨
This is the same set up as a Focus RS Golf R, A45 and the new Audi S3 rear diff. The upside is this set up is easily converted on a FWD car. The downside is that this is a part time AWD and the AWD is always slipping when engaged which creates wear. This also means they can overheat and reverts back to a FWD.
Basically the same but units are quite different in terms of control. Focus RS uses Twinster by GKN Driveline. Golf R, Arteon R, Tiguan R, AMG A45 S, RS3 and newest S3 are using Performax by Magna Powertrain.
i'm guessing the PCM has an input that tells it the car is trying to turn. otherwise it would think the outside wheel is slipping and transfer torque to the inside wheel, the opposite of what you want when turning. a torsen diff performs the same function in a different way.
Basically, in a FWD biased AWD system, when you floor it from 0, if you have a manual transmission, it will chirp in 2nd, and 3rd with the front wheels. 4th gen TL shawd experience. FWD is primary.
5:46 I wonder if rather than oil pressure locking the clutch up, maybe the oil pressure UN-locks the clutch? It might be better to have this thing fail in a locked up state. OTOH if it fails into an unlocked state I guess the other wheel can provide full thrust, as long as the controlling computer could figure out one clutch was AWOL, and you'd still be able to corner smoothly, accelerate moderately, etc.
In newer honda's the system isnt reactive but proactive. My car has a display of torque vectoring and on turns it adjusts the rear split to help the car turn better. Im guessing it uses the steering angle sensor and yaw sensor. I havemt had a chance to use it in the snow or gravel yet though.
@@speedkar99 no, the Honda isn't a differential, so a pair of locked clutches would be like a welded differential. No slip, ever, because there is no 'unlocking', so there is no end to the fun! ('twas a blast in my S13, ~20 years ago)
@@speedkar99 I just read this description few years ago. That's pretty much the same what you found in this Acura: "The Juke DOES have an open diff up front - meaning the power transmitted to the front wheels CAN effectively go 100% to one wheel if it is spinning, though I suspect the traction control system probably can and does mitigate that (to what extent I don't know). But the Juke is unique with how it deals with the rear. A driveshaft from the transaxle is always spinning a ring and pinion at the rear. Electronic clutch packs control whether or not the rear halfshafts (axles) are spinning. So the left rear and right rear torque distribution is directly controlled by the computer through the clutch packs and they are able to split the rear torque 50/50 (or 25%/25% of the total engine power) even if one rear wheel is spinning, but they also CAN put I THINK up to 100% of that rear axle torque to just ONE wheel if they want to, this mostly comes into play with the vectoring of the AWD-V setting."
drawback is you're going to loose a good percentage of power through those clutch packs just like you do in an automatic transmission.. wonder if you put too much hp through them they burn out.. i would guess so.. interesting .. good to know whats inside.. thanks
SH AWD is cool and all but it's still a front heavy car, and you'll feel it especially going downhill. At the end of the day if you put a brick in the front of a shopping cart, it's going to handle like a shopping cart with a brick in the front.
9:40 No, a locked differential is 100/100 torque split. An open differential acts as a balance and balances out the torque. When you lock the differential, the road surface and wheel speeds determine the torque. For instance, in a turn, you'll have negative torque at the outer wheel and positive torque at the inner wheel, until it's enough to break traction at one of the two wheels to allow them to turn at the same speed. How is that a 50/50 torque split?
That's the common mistake and misunderstanding, unfortunately not much people understand the torque split of an open and locked differential, usually they mess up the torque with rotational speed.
An open differential applies exactly the same amount of power to each drive wheel at all times no matter their individual wheels speeds. Hence the term differential! If one wheel is spinning on ice it doesn't take much power to do so thus the other wheel remains stationary without enough torque to move the vehicle and you are stuck. The is also the "one wheel peel" when people do burnouts. A limited slip differential does exactly what the name implies. It allows for limited difference in wheel speed. If one wheel rotates faster than the other, clutches apply braking force to the wheel spinning faster which increases power required to both wheels. Since we know a differential always applies the same power to each wheel, this increases the power output to the wheel with traction and allows the wheel with traction to propel the vehicle forward. The downsides are special fluid and special wet clutches plus the driver can feel binding or a chatter around sharp turns like a right turn onto a road. Modern cars usually use brake actuated traction control which instead of a limited slip differential employs engaging the brake on the wheel spinning faster to create the same result. A locked axle does not allow for any difference in wheel speed. Best for traction on extreme surfaces like mud and snow because it ensures power is always sent to the wheel with grip. Bad for every other situation because the outside wheel always needs to rotate faster when going around corners but it can't thus creating binding and wear. It will also cause a vehicle to lose traction around a corner because one tire must always slip around every turn. This Acura axle housing contains no differential. Instead there are two computer controlled clutch packs which modulate power from the driveshaft directly to the wheel.
A locked differential on one axle will have a 50/50 split. One wheel can be completely in the air you will NOT get "100%" torque to the other wheel (the one on the ground).
@@LexusGX460-OFF-ROAD You're citing the exact situation in which 100% of the torque goes to one wheel. The wheel in the air can't take any torque because it's in the air. If 50% is going to the wheel on the ground, where's the other 50% going? It's like if you have a double ended wrench and you put the open end on a fastener. Do you only get 50% of the torque to the fastener because there happens to be a box end on the other side of your wrench that's not touching anything?
I have a current gen RDX and when I was looking around I did not find lots of reported issues/failures with the sh-awd. It does require more consistent fluid changes than my previous Subaru did
definitely possible to bolt the transmission up to just about any civic engine. The hard part would be modifying the underside of the car and the rear suspension to be compatible with the drivetrain.
@@jacobm2625 I'm just worried that I have to connect this into the car electrical system to make it talk to the rest of the vehicle. Unless this system runs itself independently.
@@speedkar99 I disagree. Without applying the clutches, no power is transferred. The entire unit is a differential, including the clutch packs, but the ring gear carrier is a spool.
@@niuhuskieguy the issue we were having is they were braking off inside the diff flush and we couldn't extract some of them. They were just part of the diff now lol. Heavily corrosion. So honda / acura just said replace diff
You did a great job describing it! I was an engineer on the development team for this system, the pistons to compress the clutches are actually in the outside cases and the holes in the clutch hub and basket are to drain oil out of the clutch packs. Another thing to note is the RDU is over driven from the front to allow torque vectoring even when there is no difference in wheel speeds front and rear.
Great video!
Awesome! So that means the rear wheels are rotating freely until there is a demand for torque on the wheel? Can you give us a hint about the life expectancy of this system?
@@VictorIndiaDeltaAlfa Honda/ Acura has been doing this since 2005! So I’ll let your imagination run with that one.
my 08 rdx shawd still run flawlessly.. just hit 200k .. and I'm full bolt o upgraded turbo and tuned .. and there's guys making more power than me
How does this differ from the 1st gen sh-awd?
do the clutches fail into a locked state, or an unlocked state? If just one failed, could the control figure that out and keep the other one locked whichever direction you turned?
Great job breaking down SHAWD with no pretense, really well explained I learned how complicated the controls system needs to be to activate the individual clutch packs. Great job, you are a smart dude.
This is cool. I recall looking up Honda's patent filings to figure out how it actually works, back when SH-AWD came out. Now I get to see the internals.
Oh, this is way simpler than what was in the patent. The patented system has geared shafts driven by each side at 102% of their speed. Applying clutches between an axle and the shaft spinning slightly faster than the other axle allows transfer of torque with minimal loss of power.
Your presentations are spot on! You cover all relevant topics with clear understanding, but avoid wasting time. Keep on same track, cause you're nailing it.
A top channel!
One thing to note is that the RDX SH-AWD system is a simplified version of the system found in the 2nd gen RL. The system in the RL can overdrive the rear wheels upto 5.7% faster than the front wheels while the RDX overdrives the rear wheels at a constant 1.7%. The RL system also incorporates a planetary gear set within the clutch packs that allows for the accerlation of the rear wheels. Really clever system.
Yes the RL makes the rear wheels spin faster. Not good for wear but good for handling.
Ive had clutch packs explained to me numerous times. It all makes sense but at the same time it blows my mind that we learned how to make them
right like who thought of this
Smart people , thats who.
Fantastic video. If you’re worried about Phillips screwdrivers stripping screws, try a JIS (Japanese industrial standard) screwdriver. They don’t cam out and have better engagement!
Excellent point. Phillips and Pozidrive (Europe) seem somewhat interchangeable, but Phillips and JIS are absolutely not compatible. So many of us grew up thinking Phillips was shit because we stripped a bunch of screws when taking apart Japanese electronics. At the time, none of us knew the screws were JIS, and we were stripping them because we were using the wrong tool.
Amazing descriptions of complex things us mere mortals barely understand!
Glad you learned something
Old tractors have rear brakes only, with separate left and right brake pedals. You step on one or the other when you need torque vectoring, usually to make a really tight turn, or keep a slipping drive wheel from digging in deeper.
It's part of what makes them magic - the first time you see a tractor turn into a field it'll blow your mind 😀.
Toyota's "turn assist" for their Landcruisers & GX550 works that way too... brakes the inside wheel for a tight turn offroad ❤
That's not quite torque vectoring since you are braking instead of applying power
@@speedkar99 an open differential delivers equal torque to both axles, regardless of rotational velocity. Braking on one side directs more torque (and thus more power) to the unbraked side. On the braked side, some power gets converted to heat.
Subjective experience tells me it works quite well.
Mr Speedkar is a master of automotive technology. As for me, my first car, in 1959, was a 1929 Model A sedan. I like to imagine the ghost of Henry Ford viewing, with some. consternation, the complexity of modern automobiles. I think he might wonder at how the manufacturers can produce such sophisticated products at a price that car buyers can afford. And rightly so.
Agreed...there's alot going on in modern cars and you have to wonder how much manufacturing goes into making them.
I had a TL with this system, really made the car handle far better than it should have
Amazing!!! Thank you for posting this. I truly appreciate it!!!!
You are so welcome!
Beautiful breakdown! Also, I love how clean everything is inside those components! Cheers!
Yeah this is a fairly new differential
Have a 2011 RDX with the SH-AWD since new and it is still a blast to drive on windy backroads. The only real issue Ive had with the car is the waste gate actuator and the sun baking anything that's not painted metal on the outside.
It is a great car still
The K23 tur is weren't known to be reliable
@@speedkar99 got 130k on mine so far, no real issues
Very informative- I had no idea these were basically locked diffs with clutch packs that allow it to turn. Getting on the throttle on SH-AWD mid corner is actually pretty fun.
It sure will be, with any torque vectoring system.
However you can't beat a proper RWD setup
Great explanation! I have an Acura with SHAWD, new to me. Great to be shown more about it!
Glad you enjoyed it!
Great breakdown man... always wondered how Acura puts the SH in SH-AWD!
Thanks!
Instead of the Dual Pump Fluid that Honda mandates, I put Mobil1 Synthetic ATF Multi Vehicle (Silver bottle/black label) in the rear diff of a 2019 MDX. As per 540RAT engineering blog, it’s tested as having the strongest mechanical wear protection, even better than Amsoil. I also use it in the ZF transmission. This was 7mos ago. Working just as it should. Thanks for this video!
earlier G of Sh-AWD spec ATF-Z1 fluid. Honda spec DPF after ATF-DW1 took over Z1.
@@gogozy1 yes when this mindless thin stuff started taking over. It wasn’t cutting it. I also don’t believe ANY OEM fluid is good at protecting. It’s only good for lining those company pockets. 540RAT tested a bunch of the thin new gen stuff like Mercon LV, Maxlife (my old fav), Mobil Synthetic Multi Vehicle (blue bottle, not Mobil1), Castrol Transmax and they all failed with “0 psi.”
as an engineer nothing keeps me up nights like people ignoring my usage recommendations... some brands might want their product to self-destruct confident that you'll buy another (MB, BMW these days?) but I think Honda and Toyota want their good engineering to be their calling card.
@@lqr824 true but even Honda and now Toyota have gone the route of turbocharging. Maybe they have something up their sleeve but I don’t see them lasting like the current 2GR, 3UR 2UZ did..
Engineer here. I feel the same & hate neglect.
I daily drive a KB1. Never clicked on a video so fast.
Well glad you did
not too shabby, pretty good engineering
Yes except those clutches are a power loss
Great video, I love these mechanical breakdowns. I hear a lot of reviewers claim the Honda iVTM-4 is the same mechanically as the SH-AWD except the software won't do the vectoring. Would be interesting if you got a hold of the iVTM-4 to compare.
Every (ignoring eccentric cases like the eSH-AWD hybrid system) SH-AWD Acura since the 2005 RL can apportion 70% of the power to the rear axle.
Yea through some tiny ass clutches that begin to wear out from day 1
I have an AWD MDX and it makes that bigger thing much easier and fun to drive - also makes me wonder why they didnt make an AWD Integra sku. Could have been awesome - especially if they added some level of manual torque assigning, could keep it vectoring, go 50/50, 30/70 or something lol (idk if thats even really possible) but even just SH AWD would have really made the new Integra a lot more compelling, especially since Acuras is great in my experience. Could have competed as a higher end GR Corolla or something.
Unfortunately it would make the cost of the car leave the demographic they're aiming to serve. That, and the R/D of adding AWD to the new integra would defeat the purpose of the TLX. I dont think they want to invest in designing a new transmission auto or not for the civics drive train when they sell the TLX anyway. Manual SH-AWD hasn't existed since 2014 and I think this is the reason behind it.
The integra is in a tight spot. SH-AWD would be more expensive and heavier, when it's already more so than a civic SI
The recent SH AWD system has been simplified. I think the older generation has planetary gear sets in the unit to either drive the rear wheel at 100% or overdrive (+3 or 5%? forgot the exact number). Now it seems it is just single speed (overdrive) controlled by two clutch packs.
Correct. The 2nd gen RL had the most advanced SH-AWD implementation using the planetary gear set within the clutch pack that allowed for up to 5.7% overdrive.
Yes this is pretty simple because it's an RDX.
I think the old RLX/TLX would be more tuned for dynamics
Great explanation more understanding Must be expensive for parts like a lot of things Knowledge is power 😍👍👍👍
Yes this is an expensive video but all in the name of knowledge
I think the hydraulic pressure applies force from a piston in the end castings to squeeze the clutch pack. Those holes you pointed out are for lubricating the clutch faces.
Thanks, that makes sense.
Very interesting to watch.
My 2013 Mitsubishi Evolution X has a similar rear differential. It’s an open rear diff with what Mitsubishi calls “active yaw control system.” Torque vectoring pretty much for the rear wheels with an active center differential. It can send 100% of power to an individual real wheel during hard cornering. Great for the race track.
Rear unit of Evo is actually quite different. Both wheels are powered mechanically via differential (which is missing here), so even if clutches are open - it's still awd car while this one is FWD then. In Evo, power goes through gearing, not just the clutches. Evo also cannot power just one rear wheel.
@@4x4.tests.on.rollers I learn something new everyday😬
Great channel, great explanation. Thanks
Welcome!
"Like a Longitudinal mounted RWD vehicle, which [Honda] don't have." - S2000: "Am I a joke to you?"
I think he means currently in production
NSX has entered the chat
@@lqr824 Was the engine in the NSX not also transverse?
@@GrandpaRonin the newest iteration of the nsx had a longitudinal v6 whereas the original nsx was a transverse v6
Which is also… not currently in production. Canceled in 2022.
This is too cool. I install those differentials at the factory!
That's some nice design work.
VERY informative video guy! Great explanation!
Great system if you take care of it with fluid changes
I was wondering, though those clutch packs are going to wear out probably not a 300k system for sure like my toyota is
Yeah they will wear but this is a part time system
Awesome breakdown ✅Like a boss 💪🏼💯
Very interesting. Thanks for sharing. Sure some wear on that side bearing.
You are welcome
This is a really cool video! Thanks for sharing! A few questions:
1. Does the transfer case use a variable pressure-controlled clutch as well to dynamically distribute torque between the front and rear wheels as well? If so, what mechanism does it use to vary the transfer case clutch pressure?
2. How does the rear differential measure wheel torque eg: 25% left and 45% right? Does it just use oil pressure only?
3. How long do these clutch packs last? Can they be replaced without replacing the whole unit?
These types of units do not need any additional clutch to control front/rear torque split. Everything is controlled by the clutches on the semi-axles.
Badass video dude
This is amazing. Never did I think I would see a manufacture outside England take one of the most reliable parts of a car and turn it into an overly complex mechanism that surely will be a high failure point. And will never make it to 200K+ mileage with minimum maintanance like a regular diff with a limited slip inside it.
What are you blathering about? Acura's with this AWD system last forever. It isn't even a complicated system...
can we see a side by side comparison between the acura shawd and audi haldax fake quattro?
this is cool! this "diff" can turn the car into a one wheel drive :D
Actually it can't.
Thanks for the video. It was like I was right there with you. I have a couple of questions: 1) how did you get your hands on that part (the rear diff)? I heard you say it was off an RDX, but was it a wrecked vehicle? so, history and where you got it from. 2) judging from your disassembly, some of those parts cannot be reused. Was it solely for the sake of a video? Or is that part of a car that's being disassembled/rebuilt?
I really appreciate how professional and straightforward you are in this video. Being a gear-head myself and a former tech no longer working in the industry, I still maintain a very strong interest, especially with Honda/Acura. Anyways, this was an inspiring video and I appreciate what you do.
Thanks. I bought it from a part out of a wrecked 2020 RDX for teardown. I love learning how things work! Thanks
@@speedkar99did it understeer into a tree because the owner overestimated the capability of SH-AWD?
I had to change my two front tires because one couldn't be repaired. The tire salesman said I need to change all four.I have a 2021 RDX sh awd.
I wonder how this compares to Mitsus AYC on their Evos from the 90s
Glad your brother donates so many clothes for your clean up. Very interesting video.
Since you do so many automotive investigations, is there a best brand, better design, better longevity, auto that you have found.
I love your vids and approach. Keep it up.
I appreciate that!
I bought a base Prelude (5th gen) because I had heard reports of SH breaking. I installed a bullet-proof Quaife differential instead. The warranty specifically mentioned that racing wouldn't void it.
Take a rear diff module out of a wrecked Acura and adapt it to the Prelude's front axle. SH-AWD doesn't fall.
Good update keep it up the good work 👍👍👍
10:48 thermal pad, for heat dissipation as well as transferring heat to case
11:11 inductor probably is part of voltage boost circuit to drive the high(er) voltage Brushless DC motor (BLDC) for better speed and torque control.
If it's DC, why is there 3 coils?
Indeed the term used is strange. Actually, it came from the heritage that it's a revised version of its ancestor brushed DC motor. Brushed motor, although the power feed is DC, but it's internal commutator (brush) contacts change the current direction flow through the coils. Brushless version is doing a similar thing by
- change outside stator from permanent magnets to coils,
- change the inside rotor from coils to permanent magnets
- since there is no commutator by rotation to help changing current direction, so electronic circuit is used. The DC power feed go through 3 sets of simple switching transistors (just ON and OFF, including reversing the current flow direction) to drive the stationary coils .
The waveform is very simple, e.g., first phase: POSITIVE 0-120 degree, NEGATIVE 180-300 degree. The other two phases do the same with 120 degree phase offset.
P.S. a similar type of design with much refined waveform can AC Synchronous PMSM motor, typically used in EV drive motor. The waveform will be just 3 AC sinusoidal waveforms with 120 degree offset.
3 phase offers better power continuity than 2-phase motor. Nicolas Tesla's original AC power generator is a 3-phase system and the motor is also 3-phase.
Can you do a tear down on the Acura RLX Sport Hybrid? It's an electric rear diff
I'd love to get any electric rear differential
Generation 3 honda prelude had 4WS mechanical four wheeled steering,
Those were cool cars... My neighbor had one way back when I was a kid and it was cool to see the rear wheels move
Interesting, I wish you got the Lexus TVD too, its an open diff with individual brushless motors for each side and it's used only in 2 performance F cars - RC F and GS F, the GS F always had TVD while RC F Track Editions do not have TVD and since 2023 they also stopped making TVD for RC F. It has a separate ECU system for itself as well.
I'd love to have the Lexus one but I can only imagine how expensive it would be to obtain for teardown!
Quickly headed to 1/2 MILLION SUBZZZ!!!
I hope!
Trickery comes from front PTU and rear spool gearing ratios.
Yep. Very interesting design!
Interesting building block for a homemade tracked vehicle
It sure would be. But a proper RWD setup would be ideal n
非常感恩，了解，謝謝分享！
Awesome stuff, thanks for this! Will you be breaking down the front trans/differential for this system as well?
Front differential is typical for a front wheel drive transaxle. There's a transfer case that outputs power to the rear axle directly from the front differential.
you're the break down king .. it seems to be very similar to a Volvo xc90 haldex system .
Haldex is placed on a driveshaft and it powers rear axle. It doesn't power rear wheels separately.
@@4x4.tests.on.rollers concur with the objective .... should of been more specific as to relate with componentry (electric oil pump and clutches ) although Honda has a more reliable system. I've just replace my oilpump two months ago😮💨
This is the same set up as a Focus RS Golf R, A45 and the new Audi S3 rear diff.
The upside is this set up is easily converted on a FWD car. The downside is that this is a part time AWD and the AWD is always slipping when engaged which creates wear. This also means they can overheat and reverts back to a FWD.
Basically the same but units are quite different in terms of control. Focus RS uses Twinster by GKN Driveline. Golf R, Arteon R, Tiguan R, AMG A45 S, RS3 and newest S3 are using Performax by Magna Powertrain.
Yes if this was full time it would burn those clutches
@@speedkar99 Not necessarily. There are many permanent, clutch based awd systems. They just keep the clutches slightly engaged.
i'm guessing the PCM has an input that tells it the car is trying to turn. otherwise it would think the outside wheel is slipping and transfer torque to the inside wheel, the opposite of what you want when turning. a torsen diff performs the same function in a different way.
Yes, I mentioned this, the inputs are the driver's intention, steering wheel, yaw, throttle
Glad to see that the toothbrush is back!!!
It's always been there don't worry
@@speedkar99 Ha ha!!
@@speedkar99 I thought your wife would have demanded it back by now!
Basically, in a FWD biased AWD system, when you floor it from 0, if you have a manual transmission, it will chirp in 2nd, and 3rd with the front wheels. 4th gen TL shawd experience. FWD is primary.
Dude is committed. Went commando to get a grip on the screwdriver.
Yep!!
Excellent video
Thank you very much!
5:46 I wonder if rather than oil pressure locking the clutch up, maybe the oil pressure UN-locks the clutch? It might be better to have this thing fail in a locked up state. OTOH if it fails into an unlocked state I guess the other wheel can provide full thrust, as long as the controlling computer could figure out one clutch was AWOL, and you'd still be able to corner smoothly, accelerate moderately, etc.
This is primarily a FWD car, those will power the car if this rear differential failed.
Damn thing has Raybestos Z packs !
So in a sense hondas transfer case in the torque vectoring vehicles is closer to a traditional differential then hondas rear Differential
Yes
I want one of those 3 phase motor and the drive circuit.
Ok
In newer honda's the system isnt reactive but proactive. My car has a display of torque vectoring and on turns it adjusts the rear split to help the car turn better. Im guessing it uses the steering angle sensor and yaw sensor. I havemt had a chance to use it in the snow or gravel yet though.
It is still reactive in the scenario discussed in the video though.
It's reactive for traction control.
It's reactive for traction control
@@speedkar99 yes
@@speedkar99 understood
Excellent. Thanks.
You are welcome!
Had an 08 MDX, it handled and rotated far better than it had any right to.
Nice..for an SUV
@@speedkar99 Budget Macan ;)
Doesn’t SH-AWD stand for Sometimes Have-All Wheel Drive?
What is the gear ratio on the ring and pinion gear?
Notification Squad!🔥🔥🔥
Fuck yeah! Over pack those clutch packs and you've got a NSD (no slip differential)!
Yep. A locking differential like a Jeep
@@speedkar99 no, the Honda isn't a differential, so a pair of locked clutches would be like a welded differential. No slip, ever, because there is no 'unlocking', so there is no end to the fun!
('twas a blast in my S13, ~20 years ago)
Isn't this differential-less design also used on Nissan Juke AWD?
Very similar but Juke had electromagnetic control if I remember well.
I would have thought it would be a slip and grip system like any other CUV
@@speedkar99 I just read this description few years ago. That's pretty much the same what you found in this Acura:
"The Juke DOES have an open diff up front - meaning the power transmitted to the front wheels CAN effectively go 100% to one wheel if it is spinning, though I suspect the traction control system probably can and does mitigate that (to what extent I don't know). But the Juke is unique with how it deals with the rear. A driveshaft from the transaxle is always spinning a ring and pinion at the rear. Electronic clutch packs control whether or not the rear halfshafts (axles) are spinning. So the left rear and right rear torque distribution is directly controlled by the computer through the clutch packs and they are able to split the rear torque 50/50 (or 25%/25% of the total engine power) even if one rear wheel is spinning, but they also CAN put I THINK up to 100% of that rear axle torque to just ONE wheel if they want to, this mostly comes into play with the vectoring of the AWD-V setting."
@@speedkar99 Slip & grip (reactive) systems are shadow of the past. For about 20 years, programming is becoming more and more proactive.
Please help, I dropped a piece of plastic that is as long as a pinkie finger in the fill hole so will it damage the gear inside?
The gears will smash it and those pieces will clog the oil pump.
@@speedkar99 Do you recommend getting the rear differential replace now? or can I drive until it breaks then get it replace?
drawback is you're going to loose a good percentage of power through those clutch packs just like you do in an automatic transmission.. wonder if you put too much hp through them they burn out.. i would guess so.. interesting .. good to know whats inside.. thanks
Agreed, it's a wear point for sure
Interesting. Good video as always. Same as the Audi one. Same supplier? Technically is has no differential gears, so really just a spool.
Yep it's just a solid axle.
I don't think they're the same supplier...these are very different AWD systems!
@@speedkar99Audi uses almost the same unit in newest RS3 and S3.
How long will those clutches last during normal use? There's slip happening with every corner right?
They are open which means there's slip within these clutches. They are meant to slip but because there's fluid between them, they create some drag.
Dude you're hilarious, I have my brothers old toothbrush or I have my brothers old underwear. That's just really subtlety funny
Why do you have it ....?
I wonder if the adjustable hammer is metric.
I'm in Canada. Everything is in metric.
I'm very curious how this compares to VTM-4
Basically the same design.
Same hardware, different programming
IVTM4 AWD
Thanks professor
You are welcome
SH AWD is cool and all but it's still a front heavy car, and you'll feel it especially going downhill. At the end of the day if you put a brick in the front of a shopping cart, it's going to handle like a shopping cart with a brick in the front.
It sure is not a proper RWD setup
9:40 No, a locked differential is 100/100 torque split. An open differential acts as a balance and balances out the torque. When you lock the differential, the road surface and wheel speeds determine the torque. For instance, in a turn, you'll have negative torque at the outer wheel and positive torque at the inner wheel, until it's enough to break traction at one of the two wheels to allow them to turn at the same speed. How is that a 50/50 torque split?
That's the common mistake and misunderstanding, unfortunately not much people understand the torque split of an open and locked differential, usually they mess up the torque with rotational speed.
An open differential applies exactly the same amount of power to each drive wheel at all times no matter their individual wheels speeds. Hence the term differential! If one wheel is spinning on ice it doesn't take much power to do so thus the other wheel remains stationary without enough torque to move the vehicle and you are stuck. The is also the "one wheel peel" when people do burnouts.
A limited slip differential does exactly what the name implies. It allows for limited difference in wheel speed. If one wheel rotates faster than the other, clutches apply braking force to the wheel spinning faster which increases power required to both wheels. Since we know a differential always applies the same power to each wheel, this increases the power output to the wheel with traction and allows the wheel with traction to propel the vehicle forward. The downsides are special fluid and special wet clutches plus the driver can feel binding or a chatter around sharp turns like a right turn onto a road.
Modern cars usually use brake actuated traction control which instead of a limited slip differential employs engaging the brake on the wheel spinning faster to create the same result.
A locked axle does not allow for any difference in wheel speed. Best for traction on extreme surfaces like mud and snow because it ensures power is always sent to the wheel with grip. Bad for every other situation because the outside wheel always needs to rotate faster when going around corners but it can't thus creating binding and wear. It will also cause a vehicle to lose traction around a corner because one tire must always slip around every turn.
This Acura axle housing contains no differential. Instead there are two computer controlled clutch packs which modulate power from the driveshaft directly to the wheel.
A locked differential on one axle will have a 50/50 split. One wheel can be completely in the air you will NOT get "100%" torque to the other wheel (the one on the ground).
@@LexusGX460-OFF-ROAD You're citing the exact situation in which 100% of the torque goes to one wheel. The wheel in the air can't take any torque because it's in the air. If 50% is going to the wheel on the ground, where's the other 50% going?
It's like if you have a double ended wrench and you put the open end on a fastener. Do you only get 50% of the torque to the fastener because there happens to be a box end on the other side of your wrench that's not touching anything?
@@TheRetarp Open differential applies exactly the same amount of torque to each wheel, not power.
How reliable are these? How much maintenance do these need? Was there anything wrong with this one? It didn’t seem like it
He said it's not reliable but the goal was compactness.
I have a current gen RDX and when I was looking around I did not find lots of reported issues/failures with the sh-awd. It does require more consistent fluid changes than my previous Subaru did
Nothing wrong with this one.
Clutches will wear which is why it's a part time system monitors by temperature sensors.
My RCF has a TVD, takes a corner like you wouldn’t believe
Yeah I've heard those were great. Love to see more of those in production cars.
@@speedkar99 love it to death, this year is the last for production and the V8 for Lexus is officially gone.
This makes me want to buy an Acura with AWD. lol
Wondering if it's the same as the rt4wd civic
Nope.
looks like alien technology
It's simple
is the front diff the same? can it equally transfer the torque around?
Nope. Front must be fully mechanical (gearing).
Japanese quality is phenomenal
It's sure is solidly built.
Acura SHAWDY
Pulse width modulation
Yes
oooh shiny
Esta vez nos hizo esperar 10 minutos hasta que empezó a romper algo, hasta ahí iba prolijito😂😂😂
10 minutes?
I wonder if its possible to add Acura SH-AWD in a Civic
definitely possible to bolt the transmission up to just about any civic engine. The hard part would be modifying the underside of the car and the rear suspension to be compatible with the drivetrain.
@@jacobm2625 I'm just worried that I have to connect this into the car electrical system to make it talk to the rest of the vehicle. Unless this system runs itself independently.
@@htwm012 oh true, didn't think about that
@@htwm012pull the SH-AWD ECU out of an MDX or something.
That ring & pinion gearset isn't a differential ;)
Yeah it's not... The whole unit is
@@speedkar99 I disagree. Without applying the clutches, no power is transferred. The entire unit is a differential, including the clutch packs, but the ring gear carrier is a spool.
Ooof, it looks like a big mechanic bill to fix that
True. They are fail-safe though so you'd just be losing AWD.
those oil control valves are failing and breaking off inside the diff up north. all covered in rust. fix is... new diff lol
The issue was a bad batch of solenoids for the rear diff. I had it happen and they just replaced the solenoid. No full diff replacement needed
@@niuhuskieguy the issue we were having is they were braking off inside the diff flush and we couldn't extract some of them. They were just part of the diff now lol. Heavily corrosion. So honda / acura just said replace diff