1M limited slip differential information

[PyratOne]

Thanks to Dackelone for the insight, I hope he and others can add to this differential discussion. We can learn a thing or two from the M3 community as they have been dealing with ‘noisy diffs’ for a while now.

Im basically trying to determine the influence of friction modifier in the differential. Papethova and DriveHard may have some insight here - it may NOT be needed. Is it possible that friction modifier has a negative influence on differential?


Sorry for including some of the really basic stuff, I always figure more info is better than less.

where is it? Is it the exact one from M3?

Yes, according to RealOem, the LSD in 1M is exact part number to M3 with 6MT (33122283321; M3 DCT LSD has different part #!) Disclaimer here: any reference/link to e9X M3’s , only look at it in regards to differential.

What does LSD do?
Wiki link http://en.wikipedia.org/wiki/Limited_slip_differential

“The main advantage of a limited slip differential is shown by considering the case of a standard (or "open") differential where one wheel has no contact with the ground at all. In such a case, the contacting wheel will remain stationary, and the non-contacting wheel will rotate freely—the torque transmitted will be equal at both wheels, but will not exceed the threshold of torque needed to move the vehicle, and thus the vehicle will remain stationary. In everyday use on typical roads, such a situation is very unlikely, and so a normal differential suffices. For more demanding use, such as driving in mud, off-road, or for high-performance vehicles, such a state of affairs is undesirable, and the LSD can be employed to deal with it. By limiting the angular velocity difference between a pair of driven wheels, useful torque can be transmitted as long as there is some traction available on at least one of the wheels.”

1M service bulletin/fluids/schedule (MrMetak2you sticky)No need to rehash - see Metak’s sticky as reference


What fluid comes in diff originally from factory?

??? Need help here
From M3 guys: “From what I know, for earlier model years, the car came w/o FM booster from the factory. Only if you complain about differential noise will they change to fluid w/ FM booster. For later model years they may have changed it from factory, but I cannot confirm.”


How to tell if its been changed at 1200mile service?

During a recent visit to local dealer, PyratOne was told by shop foreman that one clue that diff fluid was changed at 1200 miles was the presence of a little diff fluid dribble on the outside of the diff. He says that diff are bone dry on the outside from the factory. Not sure if I believe him, just sayin.
Also, there may be clues on the nut, if the diff nut was removed it may be marked in some way.


To modify or not to modify?: that is the question

Is friction modifier (AKA “booster”, “FM”, or “+FM”) really needed? Well, according to Dackelone, they DON’T do it in Germany – may be a clue. Its possible that the chatter is not a sign of a problem, just the noise of a properly functioning diff. But the high level of complaints from the M3 community about ‘noisy diffs’ led BMW to 1) put FM in their diffs and 2) mandate FM in OUR diffs at 1200miles to PREVENT complaints.
BUT, once you put modifier in, it must stay in for the life of the car.


Why are differentials noisy, and what is “chatter”, what does it sound like?

“I have a strange rubbing/grinding noise coming from the rear end of my '09 e92 m3 that has me concerned. It only seems to occur when I'm coming out of my underground parking garage in the morning, which requires hard right turns with a little acceleration. I haven't been able to replicate the noise going left. I've only had this car for a couple months (30k total miles) and am wondering if this has something to do with the rear differential. Has anyone else had a similar issue or does anyone have any advice? I haven't called the dealer yet.”
“Hey Guys.... Ive been noticing this weird sound coming from the passenger side rear wheel. kinda sounds a bit like a low pitch rubbing ish noise. only happens when I make a right turn and if its uneven pavement. any clue??”
“I noticed it once and only once on my 2008. Circling a parking lot making tight slow right turns I could hear a rubbing sound. I thought it was something caught in the wheel arch at first. Once the car warmed up it went away and I have yet to hear it since even after trying to replicate it. My dealer will change the diff oil but I may just leave it alone.”


When does chatter start?

Looks like diff might chatter within the first few thousand miles. Some M3 forum comments about diff “But a ton of cars develop that noise. Mine started to do it with only 4K+ miles on the oil, and I drive the car like a grandpa compared to most of you here” “Note that Castrol don't make the SAF-XJ with extra friction modifiers, its a third party formulation and that Castrol generally don't recommend extra oil changes for the SAF XJ diff oil over and above the scheduled changes. Also the typical diff groan is more likely to appear in a lightly used car especially one that does most of its miles on the highway”

How did M3 folks deal with it?

This Service Information bulletin supersedes SI B33 01 02 dated March 2008.

SUBJECT
Grinding Noise from the Differential during Slow Cornering

MODEL
E90, E92 and E93 M3 from start of production

SITUATION
A grinding noise may be heard coming from the differential during slow cornering. This noise is best heard during tight cornering situations; for example, while parallel parking, driving in a tight circle, etc.

CAUSE
When the rear wheel speed differential varies during tight cornering, a slip stick effect is created on the lining and steel discs incorporated in the differential locking clutch, causing the grinding noise. This noise typically goes away as the locking clutch discs in the differential are broken in.
The break-in time varies depending on driving habits; for example, tighter cornering (working the locking clutch) means that it takes less time to break in the locking clutch discs.

CORRECTION
If a customer complaint is verified as described above on the E46 M3; E60 M5; E63 and E64 M6; or on the E90, E92 and E93 M3 vehicles, the differential oil should be replaced with a specially formulated differential oil, BMW part number 83 22 2 282 583.
PROCEDURE
1. Drain the differential oil. Refer to the appropriate model repair instruction in TIS:
Main Group 33 / Subgroup 10 / RA 0011259.
2. Refill the differential with special differential oil as shown in the illustration below.
Differential fill capacity = 1.2 liters (1.3 quarts).
3. Road test the vehicle.
With the vehicle at operating temperature, drive in tight circles (20 circles in each direction), allowing the special oil to coat the locking clutch discs.
The grinding noise will decrease when the locking clutch discs are sufficiently coated. Some slight noises may still be heard after driving in tight circles. Advise the customer that it will be necessary to drive the vehicle up to 600 miles before all noises are eliminated.
Note: Vehicles that have had the differential oil converted to this special oil should continue to use this oil whenever a service requiring the differential oil replacement is indicated.


From the M3 guys, does chatter come from both 6MT or DCT?

“the SAF-XJ fluid is the DEFAULT BMW APPROVED fluid for M3's differential (see attached). NOT ALL CARS get the diff noise using the SAF-XJ fluid. For example, my DCT never made noise with SAF-XJ, but my 6MT did”

How to check?

Tight circles, slowly. Seems like the M3 guys notice it more with small, RIGHT-hand turns.


EDIT from PyratOne: Im going to guess that with the 1200mile service on 1M including FMin diff, that we will experience less chatter than M3 crowd. BUT (big BUT), some dealers may not, have not, done 1200mile service with FM in the diff (uumm.... mine). As a whole community we will probably experience less chatter, but I suspect some may.


Links to M3Post on the subject
1200mile service bulletin for 6MT M3: http://www.m3post.com/forums/showthread.php?t=265139

Fluid quantities and types for M3: http://www.m3post.com/forums/showthread.php?t=129886

A cheaper diff fluid from MB?: http://www.m3post.com/forums/showthread.php?t=475708

A complaint of a ‘strange noise’ http://www.m3post.com/forums/showthread.php?t=608288

Complaint of ‘weird sound’ http://www.m3post.com/forums/showthread.php?t=506894

When to change diff fluid http://www.m3post.com/forums/showthread.php?t=610651

[Dackelone]

PyratOne... those Castrol bottles from MB look just like my SAF-XJ (w/o +FM) that I bought over here in DE.









I have stated before that the "+FM" that BMW NA says to use on 1M's and M3's (While BMA AG does not) is just BMW NA trying to prevent a few cars from being Lemon'd for diff noises. But that is just my gut feeling. I have no evidence about this.

I also think that when you use +FM it has got to somehow impact the way the LSD works. IF the LSD is no longer locking up at low speeds( and not making noises) then it has to be more of an open diff) function. I would be curious as to see an camparosin of two cars one with +FM and one w/o doing a drag race or going sideways thru a turn.



Btw... I found this video that explains how various differentials work in a car/truck. Also watch the video at 2:08 when they talk about an LSD and at 3:52 when they show a "auto diff" which is what we have on non M models (e-diff).

Dackel

[DriveHard]

I would say it appears as though Pyrat has nailed this.. good job by the way ..

I would like to add this to help answer the " should I or Shouldn't I Modify" question.

as Pyrat noted, and as stated in the bulletin. The Modifier is there to help condition the clutches / discs at LOW, TIGHT, turning speeds inorder to reduce / remove the agressive nature of the cluthes at that speed. As we all know, we as "spirited" drivers could give a hoot about the LSD and its performance at 10MPH in a garage... Having said that, When we "spirited" drivers do want the LSD to perform as designed, there are very large forces, and complex mechanical design incorporated into the LSD that it would not matter what modifier may be in there..

Basically im saying that the modifier fixes a low speed / low force clutch slip issue that creates unwanted noise for most in their 50k / 60k + car. and i suspect that we are getting 100% use of the LSD when it matters the most..

p.s if you want to know what the noise sounds like... find someone with an old jeep CJ and lock the front hubs and do some circles in a parking lot a little faster than you would normally go.. That snapping / crackeling noise is what you get ...

[PyratOne]

@ Dackelone "PyratOne... those Castrol bottles from MB look just like my SAF-XJ (w/o +FM) that I bought over here in DE."

Yup, looks like MB grabbed the castrol and slapped an MB sticker on it! To clarify, both do NOT have friction modifier.


@ DriveHard, thanks.
Three scenarios:
1) at 1200miles your 1M diff was "correctly" serviced with diff fluid that contains FM. Result is likely you will not hear any chatter. Also, likely no effect on function of LSD "when it counts" during spirited driving

2) at 1200miles your 1M diff was serviced "incorrectly" with diff fluid that does not contain FM. Result is possible that you will experience chatter at low speed turning, and likely a fully functioning LSD.

3) at 1200miles your 1M diff fluid was not changed. You're f-#@!-ed. Argue for new diff, or extended warranty.


Still wonder a couple things. What is the fluid in the diff original from the factory? Chatter and NO FM really OK long-term for the 1M?


This all helps explain a couple scenarios I encountered. First was at PCD when my brother and I were driving their 1M. Had a horrible noise when we slowed to make 180degree turns during excercises. Hmmmm.

the other is that ED/VPC (Edit:VPC not PCD) 1200mile service representatives are adamant they put in the right diff fluid. They're telling me (and Papethova) they put in the NO FM fluid and thats the right stuff. Maybe in Germany it is. Maybe some purists think it is. Maybe it TRULY is for full diff function. However, they (and the retarded dealer I went to yesterday) are both IGNORING THE SERVICE BULLETIN! Even after I gave it to both prior to speaking with both.

The debate is wide open on whether FM is good/bad for diff. There is NO DEBATE on what BMW NA wants techs to do at 1200mile service.

[Papethova]

A lot of GREAT info here

Good job K!!

[flzrider]

Good info. I, too, am curious about what fluid they put in at the factory when the car is built. I can easily see it going either way.

[Dackelone]

Castrol Syntrax is the new SAFXJ. I am not sure if this is only in the UK or worldwide. ?



I found this pdf on the Castrol Syntrax oil's specs...
BPXE-8F54WP_0.pdf

I found the above pdf here... look at the last post...

http://www.bmw-driver.net/Forum/show...t=30678&page=2



also this is interesting read...

Castrol SAF-XJ


Diffsonline.com lsd break-in pdf
http://www.diffsonline.com/techinfo/...break%20in.pdf



Note: as I was doing some research on the web about what diff gear oil BMW uses for a factory fill... I have seen many of the same questions by other //M owners. Going back to the e39 M5, Z4M's and e46 M3's. As far as I could determine - no one has gotten to the bottom of this mess.

PyratOne - I think the reason why your dealer was fighting you to replace teh diff oil is bc the +FM fluid is a bit pricey. I have seem posts on other forums that it can costs up to 75 UK pounds per 1/2liter! That is a lot! Also... as to your shop foremen telling you how to detect a diff oil change by some oil dripping off the bottom of teh diff... I think that would be from a sloppy tech. When you change the diff fluid... you keep pumping in fresh new fluid until it spills out of the "fill hole". You would think a tech would pray some BrakeKleen to remove the excess fluid. But most don't. Hence the tell-tale oil drip.

[bloodsales]

wow, must be useful

[nachob]

Originally Posted by Papethova

A lot of GREAT info here

Good job K!!

Gentlemen, great thread here just one small thought that was pressed upon me by the ///M folk in Garching. The unit in our our cars is a Full-lock differential. A limited slip unit reduces slip. Our unit will do 100% lock. Out of habit of calling it an LSD, I made the same mistake and was corrected more than once.

: )

[DriveHard]

Pyrat

How many miles on the diff at this point ??? just curious

p.s if you are in NY any time soon, drop me a note and we'll take a peek at your car if you want ..

Regards

[PyratOne]

"PyratOne - I think the reason why your dealer was fighting you to replace teh diff oil is bc the +FM fluid is a bit pricey. I have seem posts on other forums that it can costs up to 75 UK pounds per 1/2liter! That is a lot! Also... as to your shop foremen telling you how to detect a diff oil change by some oil dripping off the bottom of teh diff... I think that would be from a sloppy tech. When you change the diff fluid... you keep pumping in fresh new fluid until it spills out of the "fill hole". You would think a tech would pray some BrakeKleen to remove the excess fluid. But most don't. Hence the tell-tale oil drip."

Dackelone,
Could be, I really hope not. Seems like a big risk to put "wrong" fluid of any kind against bulletin recommendation. Whats the saying? "penny wise..." or is it " an ounce of prevention..."? "or is it an a penny of prevention..."?

Originally Posted by nachob

Gentlemen, great thread here just one small thought that was pressed upon me by the ///M folk in Garching. The unit in our our cars is a Full-lock differential. A limited slip unit reduces slip. Our unit will do 100% lock. Out of habit of calling it an LSD, I made the same mistake and was corrected more than once.

: )

Noted, thanks. Seems "LSD" is ubiquitous. Knowing thats is full-lock will help with the research.

Originally Posted by DriveHard

Pyrat

How many miles on the diff at this point ??? just curious

p.s if you are in NY any time soon, drop me a note and we'll take a peek at your car if you want ..

Regards

@ DriveHard, just hit 3000miles. Many thanks for the offer, but I have no plans to be in NY anytime soon. So, me and Papethova are in same boat I think. We are being told (adamantly told) the fluid was changed at VPC, but its not itemized on invoice. The only "proof" of 1200 mile diff service I have is local dealer service tech (excuse me, foreman) noting the diff fluid spillage. This is adequate documentation in their mind. Not very scientific.
It would be comical if it weren't so frustrating. Oh, I forgot to mention. When I was at the stealership, I asked if I could have the old diff fluid if they were going to change it - and they said no.

So, next step for me? Second opinion from a local BMW mechanic who is respected. I'll talk to him A LOT before I go in. My plan is to save the old diff fluid and consider having it analyzed. For what? I dunno yet. I need to find out what factory fill diff fluid is/was.

for those that are reading this and want to write "c'mon, buddy. Just put some new fluid in there and drive the damn thing!". I am gladly accepting cash from you for new diff repair in 3-4 years.

[Papethova]

Originally Posted by PyratOne

I need to find out what factory fill diff fluid is/was.

Why not contact the Leipzig plant and ask them directly?

I had contact info but I cant seem to find it otherwise Id post it here. I know I had emailed Dackel with it, he may still have it or have his own contact there since he has submitted questions to them.

My guess is its the same fluid w/o the FM and if VPC didnt put FM fluid in there I plan on continuing to use the non FM fluid. Problem is no way to be certain now.

[eeghie]

Originally Posted by PyratOne

Noted, thanks. Seems "LSD" is ubiquitous. Knowing thats is full-lock will help with the research.

.... inherent to the design of a differential are its characteristics that can vary as a function of wheel speed difference and/or input speed/torque etc.

Isn't it possible that the M3/1M diff is not a 100% open / 100% locked differential. And that it can operate under lesser degrees of locking that build up to 100% lock once a certain threshold power/speed difference is applied?

Can anyone confirm (with reference if available) what the locking characteristic indeed looks like? (even if it can only be 100% unlocked or 100% locked, at what torque, speed difference or else does the change occur?)

[Dackelone]

Originally Posted by Papethova

Why not contact the Leipzig plant and ask them directly?

I had contact info but I cant seem to find it otherwise Id post it here. I know I had emailed Dackel with it, he may still have it or have his own contact there since he has submitted questions to them.

My guess is its the same fluid w/o the FM and if VPC didnt put FM fluid in there I plan on continuing to use the non FM fluid. Problem is no way to be certain now.

I have sent the L-Werk numerous emails. I never get any replies back. I don't know IF they don't know the answer or if they just don't want to answer.

I did find a German phone number on one of the +FM bottles posted online. I think I will call that number in Munich and see what I can find out.

[richb811]

There is much win in this thread! Thanks for keeping track of all the information guys!

[EmmDrei]

Honestly guys... I seriously doubt your "lsd causes a noise" theory.

In order for a lsd to engage, especially for a hydraulic lsd, you need a difference in wheelspeeds first. By default, the lsds clutch-pack will be disengaged. If you want details, then find out which lsd the 1M actually has.

Below are the people that make the lsd (afaik) and one of their hydraulic lsds is what the 1M should have. (Page 4 of the PDF I have linked to) Once someone finds out which, then you can dig for data.

The link.

If the grinding sound is actually caused by the lsd, then the drivers experiencing it are only telling half the story. They would have to make a wheel slip before they could hear the noise. And if that is the case, then their tire is simply telling them, that the lsd is actually engaged. Normally a cars differential causes the inner wheel to turn less, than the outer wheel, as it has less distance to travel. The lsd will prevent just that and thus the INNER (contrary to the drivers reports that state, that the OUTER wheel makes a noise) wheel will turn more than actually required. Thus grind. BUT only if the lsds clutch packs are partially (partial lock) or fully (100% lock) engaged.

[Dackelone]

Ok guys... today I went to my BMW Zentrum and asked about the diff fluids for the 1M. Here is what I found out. The factory fill oil for the diff is Castrol SAF-XJ. NOT the +FM, just the regular SAF-XJ oil. This oil should be changed at the first service 2,000 kms or 1,200 miles on M cars. This oil is spec'd for the M3 e90, e92, e93 and 1er M Coupe, aka e82 M Coupe, aka 1M.

You need three 500ml bottles to change the diff oil out. The diff holds 1.2L

Castrol SAF-XJ BMW part number: 83222282583 for one 500ml bottle. cost is 24 euros per bottle at my BMW Zentrum.

I also asked about the Castrol SAF-XJ+FM diff oil. My dealer had never heard of this +FM stuff... but it is a good part number. The price of +FM is 30 euros per 500ml bottle. But it is interesting that BMW AG does not say to use it. At least not in their latest service info to the dealers over here.


I have scan'd the service document(that I got today) for you 1M guys. At the bottom of the first page BMW AG also lists other diff oils that you can use in place of Castrol SAF-XJ.


hinterachsgetriebe öl = rear differential gear oil








SAF-XJ +FM (plus Friction Modifier) some fotos I found on the net of +FM...

[SpencerMH]

I have noise from my rear diff as described, if the noise does not bother me is it still important for long term function to have the fluid changed?

[Dackelone]

Originally Posted by SpencerMH

I have noise from my rear diff as described, if the noise does not bother me is it still important for long term function to have the fluid changed?

Your diff fluid should have been changed at the 1,200 mile service! You had that done - right?

BMW NA position is to not change the trans fluid at 1,200 miles. And only in the US. BMW for the RoW says to change the trans fluid at 1,200 miles.

IF you had the diff fluid changed and its making some noises at low speeds - that is pretty much normal. You could have BMW NA change your diff fluid to the SAF-XJ+FM fluid to quiet down this noise. Even with the non +FM diff fluid, I don't think any damage is being done. Alot of diffs make that kind of noise.

You could go to an empty parking area and do about tweety turns (circles) to the left and then tweenty to the right. All in 1st or 2nd gears - low speed. That will make the noise happen (ie clutch dics in the diff working) and cuase some wear. This should break in the diff - enough to stop the noise. Even when BMW switches a car to +FM fluid... you need to do that procedure to coat the clutch discs in the diff. Then the diff won't make that noise anymore. I suspect even doing so without +FM in your diff would cause enough wear to stop that noise.

I think we should hear from someone in the service dept like DriveHard (Alex).

[SpencerMH]

Yes the 1200 service was done and the diff fluid changed. I will try this parking lot break in procedure and see if that quiets it down. I'd rather deal with the noise the remove the piggyback for a service stop so no biggie either way, I just wanted to verify I wasn't damaging it. Very good thread, thank you for the help.

[rapter]

mine is at 13000km and it has started to grind... service book on Friday to remove fluid and pack with correct fluid plus additive. More to come following new break in period of approximately 1500 kms.

[rapter]

Originally Posted by rapter

mine is at 13000km and it has started to grind... service book on Friday to remove fluid and pack with correct fluid plus additive. More to come following new break in period of approximately 1500 kms.

Update

After break-in period of friction modifier the grinding was completely gone- great ! However there was a new ticking metallic meshing noise that manifested on hard right hand Turns.

The harder the turn (right) the more the ticking. Dealer has ordered a new "factory refurbished diff" for installation in my car.

Any thoughts on what the metallic ticking meshing at high speeds are? Are they harmful for the longer term ?

I would preferably to keep my diff if there is nothing wrong with it.