BMW M-Diff Locker Explained
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- Опубликовано: 20 июл 2018
- BMW Regulated Rear Axle Differential Locker (M-Diff). I'm often asked about the controller I'm using. I'm using a FutureKit Small motor PWM modulator similar to FutureKit Model FK823. More information can be found here. www.amazon.com/Motor-Control-...
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Beautifully presented and narrated. You simplify what is normally complicated to understand. Straight to the point, no bullshit, no attempted humour like others, no fluff. Brilliant. 10 /10
Cannot thank you enough. You are doing this world and engineering world a favor. Appreciate your efforts and German engineering.
Everything has such a simple solution, when you think about it after it's figured out, but then the implementation is what makes the simple stuff soooooooooo complex. What a masterpiece.
No one has explained it better. Thank you for creating this video!
I was really lucky to have someone donate a few of these to me plus the technical info. I really gave me a change to dissect it for this educational video. I'm glad you enjoyed it.
Still very informative after years, glad to see more!
Thanks for the very thorough explanation. I wondered how the M diff works.
Very great video! Nice differential progress and very useful explanation.
thank you, I've been searching for that explanation a long time
Amazing explanation of how this functions and easily understood and remembered. Thank you for making this video I can now tackle my issue with confidence. 🤩💯👍
Superb teacher.
German engineering 🇩🇪😍
@@lada_niva_1.7i no one said American engineering was bad, chill
Garbage engineering
Best video i ever seen for m sport diff
Thx
Thanks
Great video
AMAZING.
Thx! Very helpful info.
I am currently looking to replace the stock diff in my ‘15 M4 due to constant overheating issues while raced on track.
Idea is great, unfortunately when pushed hard the 3 temps sensors ultimately open up the diff completely in the middle of the apex and you end up with a bonfire of slicks after couple of laps. It’s a shame cause old school LSD’s like drexler are lot more track biased and not really suited for everyday driving and Wavetrack type biasing lsd’s can never fully lock… 🤷🏻♂️
yea, this diff is not designed for anything past everyday driving and used when the ground is slippery. Rain, snow, ice, etc..
you might need to make a cooler/pump for it, only ever had to do it for gear boxes though. Other possible options include over filling or perhaps they make a larger aftermarket "sump" or sump extension
Hi there and thank you for this great video. Is there a way to calibrate the locking mechanism? . Reason I ask is because we changed the rear diff cover and rotated the gear that connects to the motor or module that locks the rear diff and now the car is showing a rear diff lock message. The gear that you show that adjust the pressure of the plates on the m340 is half gear and the other half is blank, basically we left it in the blank spot . Thanks in advance
As far as I know these are swap out units and not designed to be rebuilt or swapping out parts or the housing. Not that I couldn't be done on some level but I know of now way to calibrate it if it didn't get put back together exactly as it came apart.
Thanks a lot @DrivelineMaster !!! I'm thinking on installing an M-performance (not "M) Diff for M140i. First video that explains things! As around 400 NM are on the wheels, the ~75 foot pound means ~100 NM of locking is available, if understoood correctly, this will allow the diff to have 150NM in the less traction wheel and 250 NM in the other. However the total locking torque will be different for the M-performance, right?... thanks a lot!!!
@drivelinemaster thanks for the video! Any idea on locking NM or soft powerdrifting capabilities on M Performance diff?...
I just reviewed my video and I don't see anywhere where I have mentioned how much torque the locker can hold so I really don't have an answer for you. I also don't know how it will work for power drifting. My guess is that BMW designed this for everyday driving and drifting would push it to the limits and not likely hold up over time.
Hey. Great explanation, love that. So you steering preload with pwm signal. When applying 100% PWM then diff is locked, but what if you cut off power to the motor. Will it stay in locked position? I'm concerned about engine overheating in situation when diff is locked for a long time
I'm not 100% certain but 99% certain that when you lose power to the motor the differential will have a default where it resorts back to 100% open differential. So I don't think the diff will stay in the locked mode. Please note that the diff will have various levels of being locked up such as 70%, 80% and so on of being locked. It does not need 100% PWD to be locked up.
@@DrivelineMaster thank you very much :)
Do the clutches ever need replacement because those look very hard to remove without getting the motor and other electronics out of the diff.
These clutches are not replaceable. If they were out the whole differential or at least the case will have to be replaced.
Great video! Can it provide genuine 100% lockup e.g. during an axle-twister on a X5? (To compare, a LSD can't "bite" anymore beyond a certain point, and then start slipping again like an open diff. Whats the case with a M-Sport diff-lock then?)
LSD Diffs that use clutch packs and cones have bite limitations cause by exceeding the friction limits between the friction disks or the cone surfaces. The M-Diff is also a clutch pack design but the friction is managed by the clamping force from the electric motor and ball ramping mechanism. This of course is all controlled by the computer system using various inputs. If you bypass the computer system with a PWM (Pulse Width Modulation) control board to control the position of the electric motor you will use a constant force on the disks. If the difference in rotational force for each wheel exceeds the friction between the disks then slippage or bite break away will occur. Break away or exceeding the bit limit is directly related to the electric motor position so it theoretically possible to dial in various break away limitations.
@@DrivelineMaster Thanks!
Tq
great vid, how is the crow wheel fixed to diff ? cans see any bolts ? im wondering about ratio changes, cheers
Please clarify. I'm not sure what you are calling a crow wheel. If you are talking about the ring gear then there are bolts. You just can't see them.
@@DrivelineMaster sorry, in uk we call them crown wheels, great there are bolts, many thanks for reply
Thanks. I knew that you just left off the (n) in crown and I didn't figure it out.
My diff in my 2004 m3 is leaking everywhere. I heard that bad bearings in these diffs will make all the new seals go bad fast and leak again. I’m also in the Bay Area in Hayward. Can you please help me or any recommendations
Bad bearings or misadjusted bearings can make seals leak but if they are bad you will hear them howling and making noise and they don't just become misadjusted. This only happens if someone has been in there making repairs. All Diffs have a vent of some kind. if the vent is plugged up it will blow out the seals. New or old. I would not be able to repair your leaking diff. Locate a competent shop preferable one that specializes in BMW's. Google ASCCA and use the shop finder. This is a group of independent repair shops that pride themselves on being honest and preforming quality repairs. Good luck.
Awesome video. Do you have the servomotor pinout description you could share?
Unfortunately the wires could be different from year to year and model to model but here is what I know and you can do some pin checking. Two of the wires control the motor. Those are most likely large diameter wires. They may also be shielded inside a sheath. Unplug them and check with an ohmmeter for low resistance through the motor. There are two thermistor temp sensors. two wires each. You should be able to unplug and use an Ohmmeter to pick those out. Each temp sensor should have a voltage wire from the control module. I'm not sure if these are 5V or 12V or something else. There are 2 hall effect position sensors using 4 wires. One wire supplies voltage from the module again this is most likely 5V but I'm not certain. One wire is a ground return and the other two wires should be on/off hall sensor wires. If you send me your year and model I can see if I have the wiring diagram.
I bought a 2017 M3/M4 differential from F80/F82. Will be swapping it to the E36 together with the whole rear suspension.
I'm working with a friend of mine to prepare a Control module that will set up 0, 25, 50% and full lock 😉 Any tips will be appreciated!
In that case I think you only need the two motor wires to control the amount of lock or slip. It should be easy to identify the motor wires.
So the servomotor will stop automatically in the end positions and here is no danger of breaking it?
And the 25/50% lock should be done by inspecting how much time is needed to reach the given lock?
Thanks a lot for the support!
The motor is controlled with a fixed frequency duty cycle controller. 100% on power or 100% duty on will be 100% locked. 50% duty on will be 50% locked and 25% duty on will be 25% locked. Someone needs to build you a controller where you can choose which duty cycle you want. Then it stays at that duty for the whole time that you want that specific amount of locking.
well thats quite interesting, i might be able to make this work without wiring it to the cars modules and run a standalone pwm controller with a potentiameter. do you know what type of potentiameter you used? like does the motor run on 12v or it takes more? and im guessing it probably doesnt take more than 40 amps cause most car motors like radiator fans and window motors run 40amps max
I'm sorry I don't remember the specifications on the POT I used. If I find some time I will take it apart and get those specs for you but that might be a while. Yes, 12 volt circuit and I believe I'm using a 20A fuse for circuit protection and it has not popped. If you hard wire it you will most likely get a code unless you get a second motor and strap it up some place and connect the harness to it. You might be able to fool the system that way. Then hard wire your own controller that connects to the motor that will control the lockup.
@@DrivelineMaster my car won't throw a code cause 1: the car didn't come with an lsd so car is not coded for that. 2: its won't mess with the abs system cause if there is no weird wheel spin the car will be fine
That's great but if your car didn't come with this diff I personally wouldn't recommend it. You are better off going with another type of locker or limited slip design. Less hassle and more reliable.
@@DrivelineMaster the only problem with going with a different locker is there is nothing out there that performs like the oem unit and actually locks the diff. there are options of helical gear type lsd but those don't work on zero traction situation where as the bmw locker can be locked manually with a click of a button and you have 50/50 split in the rear. oh and aftermarket solutions cost around £1400 where as i can source the bmw diff and cv axles for around $800
fyi for anyone reading this thread, this swap will only work with a 50i models cause they have the v8s the gear ratio on the bmw locker is 3.91 (so your rpm at cruise speed is gonna sit a lil high) for the front and rear where as on a lower model such as the 35i and 50i bmw uses 3.15 ratio so 1: anyone trying to do this swap would have to change the front diff aswell along with the axles and wheel bearings and for rears you might need a custom drive shaft if the difference between the oem driveshaft and bmw locker is more than 10mm cause your oem bmw driveshaft can slide +/-10mm . also for rears you'd need the cv axles and wheels bearings. subframe stays the same. after the hardware is all sorted and you manage to manually control the diff locking motor boy oh boy you'll have one hell of a ride.
Thank you for this videos. Can you tell me how the electric motor on the diff works? Is it a dc motor? How much curent does it draw ? I wanna controll it with a aftermarket ecu and a pwm module. I fugred you know since you made it work with a potmeter😊
I used a 12 volt battery and a PWM controller that can be purchased through any hobby magazine for and RC car. I don't remember the frequency but I can check next week.
@@DrivelineMaster thank you😊
Did you look at this? Do you have the pinout on the motor? Not so much info om this online. So i am very grateful for your answer😊
I'm sorry I did not check the frequency. I will try to remember to do that this week. Please note that I do not have a vehicle to measure the frequency that BMW is using. I can only provide you with the frequency of the controller that I'm using.
@@DrivelineMaster no problem. The frequensy you use and the pinout is what i need👍😊
Hi, you wanne share how you controlled the servo motor ? is fixed frequentie and regulated PWM ? do you swap + and - when you change direction ? or does it go back to start position if you set PWM lower ?
Yes, you are correct. I believe I used a Radio Controlled (RC) car controller board that I purchased online at one of those electronic stores that sells kits and such. It's been a long time. The frequency is fixed with a variable duty cycle. The tension on the compressed disks return the motor. The direction does not have to be reversed on the motor. I can't remember what frequency I used.
@@DrivelineMaster thanks great !!! I am building this differential In a restomod BMW 2002 with b48 engine 8hp50 gearbox and m2competion M active differential. Will try to figure out the position sensors to get a pid controller working
Good Luck. You might just want to run this in two modes. Locked or unlocked in which case you won't need to vary the duty. A fixed duty when you want it locked and no duty when you want it off. You could also have a push button controls that you can choose 0, 25%, 50%, 75% or 100% engaged with off and 3 other fixed duty's. That way your not guessing with a control knob.
@@DrivelineMaster thank. The push button is good option as we have canbus keypads.
I realize this is probably a whole can of worms but would it be possible for a non-M F10 to utilize this system? I'm mainly referring to the computers. Would the front electronic module on a (for example) 550i be able to connect with the GHAS?
you are correct in the fact that that would not work. The only way would be to make a manual controller like I did and manually control it yourself which I don't think makes any sense.
@@DrivelineMaster drift mode button lollll
Absolutely. No special controller needed. Motor full on or full off with a switch. You might want a current limiter so you don't burn up the motor.
Do you have a link to the PWM controller you used? Or details on what frequency, amp, etc?🙏
I'm sorry I don't have that information. I got it from Amazon and it's a generic Kit for PWM controlled motors like what is found in an RC car. If you need the specific frequency write back and I will check in next week when I get a chance.
@@DrivelineMaster it would be a massive help to know the frequency of your PWM controller. Any idea what frequency BMW uses as standard?
I'm more than happy to give you the frequency of my controller but you must know that I have never tested the frequency that BMW is using because it wasn't relevant to make my demo work. If you want to install a controller into a working vehicle that might be important. I do know the motor works with the frequency of my controller. I will have access to my demo this week. I will make some time to measure the frequency for you.
@@DrivelineMaster that would be amazing pal. I've only got the diff, so unfortunately measuring the signal freq from the BMW itself wouldn't be possible - unless there's some way of measuring from the motor? After watching this video, I fabricated an M4 rear subframe and diff onto my E30 😂. All I have left to do is figure out how to control it 😁
Did you manage to figure out this & get it working? 😄👍@@domhickman6204
So can I install it on my F30 with a Jerry-rigged "locker" switch in the cabin?!?
Technically, Yes as long as it will bolt in.
i can find the F10 M5 diff, subframe, axles and controller on ebay. i also have ista+, ista p, and other diagnostic and coding software. have you ever heard of anyone attempting to retrofit the locker into a non-m chassis, like a F10 535?
I'm sorry I have not heard from anyone else who wanted to retrofit this diff into a non-M Chassis. I have had several viewers who wanted to manually control the M-Diff.
@@DrivelineMaster manual control is actually not a bad option. at least from my perspective i could see myself dialing the lock in as traction permits and fully lock on a launch or if i am trying to drift. should be pretty easy for me tobang out a controller box.
Could I use potentiometer to specify exactly the lock I desire for my driving behavior? Instead of trusting the computer to do it, manually set lock or partial lock.
I suspect you can but you need to use your own controller to control the motor. I don't know if you will get codes or not for disconnecting the diff.
@@DrivelineMaster thank you. Yes, I'm not worried about the codes. Could you point me to the direction of the potentiometer you have used?
I purchased a project box, potentiometer, and a PWM circuit board. I'm going to have to take it apart to find that info. I will try to do that next week and post that information. Your not the first to ask about my controller. I should have posted it when I first posted the video. I didn't realize the interest in bypassing the OE computer system.
@@DrivelineMaster that would be so awesome! Thank you so much!
How much current should go into electric engine not to kill it? I want to retrofit m diff to non m car
I'm a little unclear as to your question. When you say electric engine do you mean the electric motor for the M-Diff? If you don't want the diff to ever be locked up or even partially locked up then just unplug the motor. If you care to rephrase your question I will try to answer it.
Do you by any chance know who supplies those to BMW?
There are no markings on the units to indicate the supplier. I'm sorry I do not.
GKN?
Is this for 650i as well (e63 e64) non M
This one came out of an M series. I'm sorry I don't know if BMW has ever put this differential in any other models.
What is the voltage input in each position=
The voltage is constant and I suspect battery or system voltage but I did not get a chanced to measure it. The frequency is also constant around 500 Hertz but to be honest I did not have a chance to measure the actual frequency BMW uses. The kit I used was a 500 Hertz PWM controller kit. It's the duty cycle that gets changed for each position. I did not measure the duty cycle because the vehicle can adjust that duty cycle from 0% to 100% and anywhere in-between depending on driving conditions.
@@DrivelineMaster It would be interesting to install that diff in a normal BMW and then use a controller to manually control the diff
Yes, I suppose that is possible.
Great video.... does this type come on a 2011 F10 (550i) with sports package
I'm sorry I don't know if it comes on the F10 (550i).
hi, can you gime me any info from pwm controler type? how can change the direction of engine? olny with pwm duty? thanks in advance!
I'm not sure what your question is. You can't change the direction of the engine. The PWM controller I'm using was purchased from an electronics hobby store online. Look for one that can handle the larges amount of amperes. I don't remember the frequency I used. I then mounted it into a hobby box with a Potentiometer.
@@DrivelineMaster ok, the question is,,. When the diff loses the friction disc the eléctric engine turn anticlockwise and for tight the friction disc the eléctric engine turn clockwise. How it's made? You need to change the polarity of eléctric engine? Or the clutch pack attachment system have a spring for go back to initial position? Thanks sorry for my English!
The electric motor does not reverse direction. The PWM controller determines the amount of amperage that is applied to the motor. A specific amount of amperage determines the rotational position for the armature inside the electric motor. The tension from the discs being squeezed together act as a form of spring to retract the electric motors rotational position when PWM current is reduced. I hope this helps.
@@DrivelineMaster yeah! Thanks a lot! I'm working on this differential for assembly in a bmw E30. Thanks!!
@@oriolmarti286 I'm doing the exact same thing in an E30 at the moment. How did yours come along? Did you manage to get it working?
Hello great video,you can please send me the pin out of the connector .
I think bmw use this diff on new supra😁
Sorry I don't have the pin out handy. If I get a chance over the next few weeks I will see what I can come up with and post it here.
do diode mode first find the ground. Also give very small voltage to ground see on other pins if the value almost equal to value that like maybe 1 volt so means is it power and the rest can be pwm input
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Can a stock BMW drift like japanese cars? Incredible how this works!!!
I don't think so but I'm not certain. I suppose if someone is really creative there might be a way to hack or bypass the electronics to force the diff to lock specifically for drifting.
Yes. It will power oversteer
Depends which BMW model and year. After the e36 LSD only came in M series cars. Otherwise it’s and open diff.
Do you sell bmw rear differentials
No, I'm sorry. I'm in Education.
I have a m3 2015 that I bought brand new. I keep getting a rear differential error message saying my lsd might not be operating correctly. Can u help if I get it pulled and shipped to you?
Sorry, I don't do that and would not be able to help. I suggest a qualified shop and technician to actually diagnose the problem correctly. It could be as simple as an electrical connector not making a good connection. This would cost way less than overhauling a diff. BTW, those diffs are not overhaul-able unless you just want to change the ring and pinion gears or some bearings. The LSD part does not come apart and there are no replacement parts.
How long does the multi-disc clutch last ?
I'm sorry I don't have any history on this plus this technology is not that old. I would suspect if the differential is not abused and the oil is serviced when it is recommended that the discs will last a long time, maybe even life of the vehicle.
Any idea why I am getting a rear differential error message on my f80
No clue. If it's like many computer controlled automotive systems a scan tool may be required to read a diagnostic trouble code. This code provided clues as to the fault and where to start looking. That would be the first step.
@@DrivelineMaster where are u located? What diff is that in the video u are working on?
San Francisco, Bay area. This Diff was given to me a few years back. BMW had a recall and they were changing these out. I think it came from an M5.
@@DrivelineMaster Hi, thanks for this video. Are you located in the Bay Area? I own an F80 M3. It's been making this whining gear noise for awhile and looking for help. It doesn't seem to affect performance, or atleast not yet. Would you be able to help me find out what might be wrong with it? I'm looking replace it being out of warranty, so I'm looking for options and some good advice. Thanks.
I am in the SF Bay Area but only have time to help via email or correspondence via RUclips. BMW had a big recall on these diffs a while back. That is how I got a hold of this one. Have you checked to make sure yours doesn't fall under a recall or warranty replacement? That would be my first stop and don't be afraid to complain to the factory representative if you don't get any help from the dealer. The factory representative can authorize full or partial cost assistance. Your noise needs to be properly diagnosed as being in the diff in order to get the factory involved and this will have to be done at the dealer. If that doesn't work the next step would be to replace the lubricant with the correct recommended fluid if there are no diff related codes and see if this fixes it. If that doesn't help try to notice under what type of driving conditions is the noise the loudest. Is the vehicle cold or hot, accelerating or decelerating, light throttle or heavy throttle, driving straight or making a turn, slight turn or sharp turn, etc.