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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Sat, Dec-16-2017, 09:12:08 PM   #41
Paulo M
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Default Re: Adjusting Diff backlash

Thanks for that explanation schoonerm3

My car for the first 20k miles of ownership didnít have m clunk that I was aware of. After a full rear end refresh, the m clunk appeared (or at least finally became noticeable). Even replaced entire driveshaft and clunk is still there. Either my rear end was so worn the clunk was not present initially or the rear end refresh was installed incorrectly. Guess Iíll never know.
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Old Sat, Dec-16-2017, 09:19:36 PM   #42
schoonerm3
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Default Re: Adjusting Diff backlash

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Originally Posted by Paulo M View Post
Thanks for that explanation schoonerm3

My car for the first 20k miles of ownership didn’t have m clunk that I was aware of. After a full rear end refresh, the m clunk appeared (or at least finally became noticeable). Even replaced entire driveshaft and clunk is still there. Either my rear end was so worn the clunk was not present initially or the rear end refresh was installed incorrectly. Guess I’ll never know.
Diff bush?
Pinion diff seal done?? Possible diff preload upset
CSB preloaded?
Possibility output shaft cv joints were damaged during refresh.
Rear diff bush bolts the old style
Was it new driveshaft? If not the cv joint on both could be weak
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Old Sat, Dec-16-2017, 09:39:56 PM   #43
Paulo M
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Default Re: Adjusting Diff backlash

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Originally Posted by schoonerm3 View Post
Diff bush?
Pinion diff seal done?? Possible diff preload upset
CSB preloaded?
Possibility output shaft cv joints were damaged during refresh.
Rear diff bush bolts the old style
Was it new driveshaft? If not the cv joint on both could be weak
Yep, all of that refreshed and then some. Driveshaft was bought as refurbished tho. Not sure if installed incorrectly but my car clunks like a lot of m3’s I’ve driven (just much, much smoother). I can easily drive clunk free without even trying now and occasionally get it only on slow parking lot drives (before I can’t replicate a clunk even if I tried lol). So I assume install was all good.

My car initially and few other m3’s I’ve driven didn’t clunk tho, so I really don’t know which is “normal” or not. Either way I’m done spending $ on refreshing this damn car, just going to enjoy it now or buy “fun” mods.
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Old Sat, Dec-16-2017, 10:31:22 PM   #44
schoonerm3
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Default Re: Adjusting Diff backlash

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Yep, all of that refreshed and then some. Driveshaft was bought as refurbished tho. Not sure if installed incorrectly but my car clunks like a lot of m3ís Iíve driven (just much, much smoother). I can easily drive clunk free without even trying now and occasionally get it only on slow parking lot drives (before I canít replicate a clunk even if I tried lol). So I assume install was all good.

My car initially and few other m3ís Iíve driven didnít clunk tho, so I really donít know which is ďnormalĒ or not. Either way Iím done spending $ on refreshing this damn car, just going to enjoy it now or buy ďfunĒ mods.
I think what your describing now is normal. I can do that also. I bet its flywheel slap.
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Old Sat, Dec-16-2017, 11:42:06 PM   #45
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Default Re: Adjusting Diff backlash

I'd leave it alone/keep it stock unless you know the design. Hypoid/helical bevel gearing is tough to predict contact pattern by any other means than physically checking it (paint the gear teeth, run them together, and do a visual). Tightening up the gear mesh without binding it I guess you'll be fine but I think for most of us that is tricky (mechanical +1). The gear mesh may have been designed to have optimum contact pattern with a given backlash so tightening it up could shift the contact to something less than stock/optimum (heel/toe contact reduces longevity).
That said, if longevity is not a concern, then shifting from stock should not be a worry.
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Old Sun, Dec-17-2017, 12:23:35 PM   #46
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Default Re: Adjusting Diff backlash

I have opened 2 of these LSD's.


I would personally forget about the shimming of orbital gears. The orbital gears have a concave shim on the back of them already that makes contact with the housing and the back side of the gear itself. I noticed them same amount of wear in both LSD components and while its not bad , its still a fair amount when compared to how the ring gear and pinion wear.

The is some grooves in the gear contact between the bevel and planet gear. I wouldnt attempt to shim is because I think you will increase the wear rate and friction between them. BMW have bulletins from when the car was new to say that a noise in the driveline is normal and not to be "fixed" tampered with in other words.







Shim can be seen on the back of the planet gear here

Last edited by schoonerm3; Sun, Dec-17-2017 at 12:29:26 PM.
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Old Sun, Dec-17-2017, 06:09:16 PM   #47
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Default Re: Adjusting Diff backlash

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Originally Posted by voyager006 View Post
I'd leave it alone/keep it stock unless you know the design. Hypoid/helical bevel gearing is tough to predict contact pattern by any other means than physically checking it (paint the gear teeth, run them together, and do a visual). Tightening up the gear mesh without binding it I guess you'll be fine but I think for most of us that is tricky (mechanical +1). The gear mesh may have been designed to have optimum contact pattern with a given backlash so tightening it up could shift the contact to something less than stock/optimum (heel/toe contact reduces longevity).
That said, if longevity is not a concern, then shifting from stock should not be a worry.
Proper Ring gear/pinion gear backlash is CRITICAL to the gearset longevity! I wouldn't deviate from the factory specs. But I wouldn't hesitate to shim up some of the excess clearance in the spider gears.
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Old Sun, Dec-17-2017, 06:25:37 PM   #48
nowanker
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Default Re: Adjusting Diff backlash

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Originally Posted by schoonerm3 View Post
I have opened 2 of these LSD's.


I would personally forget about the shimming of orbital gears. The orbital gears have a concave shim on the back of them already that makes contact with the housing and the back side of the gear itself. I noticed them same amount of wear in both LSD components and while its not bad , its still a fair amount when compared to how the ring gear and pinion wear.

The is some grooves in the gear contact between the bevel and planet gear. I wouldnt attempt to shim is because I think you will increase the wear rate and friction between them. BMW have bulletins from when the car was new to say that a noise in the driveline is normal and not to be "fixed" tampered with in other words.







Shim can be seen on the back of the planet gear here
Those are some great pix! Thanks for posting them up.
That is some nasty looking wear on the gear teeth. My vote on the actual cause if this whole issue goes to improper manufacture. Perhaps substandard steel in the gears, or poor heat treating? Or maybe the design of the carrier doesn't allow adequate lubrication internally?
I firmly believe that BMW's statement about "normal operation" was specifically made to disallow warranty claims for replacement diffs. This issue arose while BMW was in a warranty cost crisis from the E60 series.
As long as they wouldn't actually 'fail' during the warranty period....
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Old Sun, Dec-17-2017, 06:39:55 PM   #49
schoonerm3
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Default Re: Adjusting Diff backlash

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Originally Posted by nowanker View Post
Those are some great pix! Thanks for posting them up.
That is some nasty looking wear on the gear teeth. My vote on the actual cause if this whole issue goes to improper manufacture. Perhaps substandard steel in the gears, or poor heat treating? Or maybe the design of the carrier doesn't allow adequate lubrication internally?
I firmly believe that BMW's statement about "normal operation" was specifically made to disallow warranty claims for replacement diffs. This issue arose while BMW was in a warranty cost crisis from the E60 series.
As long as they wouldn't actually 'fail' during the warranty period....
Ya I have no doubt BMW were covering their ass.

Inadequate lubrication I believe is a thing for sure. My hypothesis on the lsd being noisy is because inadequate lubrication. When I took apart those LSD's I noticed that the surfaces between some of the clutch plates were dry in the inner most part of them but lubed on the outer perimeter and it definitely seemed to me that oil was not getting in between the clutches. This would explain the noise and would also explain how a friction modifier would get oil in there and reduce the noise.

It is worth mentioning that I have one of those LSD's fitted to my car with a 4.1 and its 100% functional and no weird noises.
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Old Sun, Dec-17-2017, 07:18:54 PM   #50
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Default Re: Adjusting Diff backlash

The diff clunk is driving me crazy after rear end overhaul. Taking it into a shop this week and if its still there I'm considering just upgrading the diff all together. Will prolly call diffsonline and talk to them about options.
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Discussing Adjusting Diff backlash in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)