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-   E46 M3 (2001-2006) (http://www.m3forum.net/m3forum/forumdisplay.php?f=9)
-   -   Adjusting Diff backlash (http://www.m3forum.net/m3forum/showthread.php?t=594514)

TheCoder Thu, Dec-14-2017 07:06:29 PM

Adjusting Diff backlash
 
Hey fellas,

Ive been experiencing the m clunk and i narrowed it down to the diff. i am certain it's the backlash. Ive been doing some Research and the process seems straight forward.

1. Remove output flangs
2. Remove diff cover
3. Remove the ring, carrier and shims
4. Remove the pinion
5. Replace the crush sleeve
6. Install and Preload the pinion gear to spec. Install new seal.
7. Install the ring gear and carrier, install shims as needed while measuring backlash
8. Verify ring runout and adjust shims as needed.
9. Verify breakaway torque of input flang
10. Install output flangs with seals
11. Install diff cover and seal.

Ill use an inch lb torque for preload verification and dial indicator.

1. Am i missing any critical steps here ?

2. Can i reuse my existing shims ? Do i need a new set?

Thanks



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Obioban Thu, Dec-14-2017 07:08:48 PM

Re: Adjusting Diff backlash (eliminate M clunk)
 
I would suspect there's a reason it's there.

It was there, from new, from the factory, in every e46 M3. BMW/M knows how to set backlash. Clunking does not fit in the BMW corporate image. If it could be eliminated by changing backlash without negative consequences, I'm fairly certain they would have done so.

Per wikipedia,

Quote:

Reasons for the presence of backlash include allowing for lubrication, manufacturing errors, deflection under load, and thermal expansion.
lubrication and thermal expansion are both quite important to our diffs.

IMO don't **** with it.

TheCoder Thu, Dec-14-2017 07:18:00 PM

Re: Adjusting Diff backlash (eliminate M clunk)
 
Quote:

Originally Posted by Obioban (Post 1067760243)
I would suspect there's a reason it's there.

It was there, from new, from the factory, in every e46 M3. BMW/M knows how to set backlash. Clunking does not fit in the BMW corporate image. If it could be eliminated by changing backlash without negative consequences, I'm fairly certain they would have done so.

Per wikipedia,



lubrication and thermal expansion are both quite important to our diffs.

IMO don't **** with it.

I realize backlash is there for a reason. My backlash is out of spec though. I am not trying to eliminate it, I'm trying to reset it to spec.

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Obioban Thu, Dec-14-2017 07:25:40 PM

Re: Adjusting Diff backlash (eliminate M clunk)
 
Quote:

Originally Posted by TheCoder (Post 1067760254)
I realize backlash is there for a reason. My backlash is out of spec though. I am not trying to eliminate it, I'm trying to reset it to spec.

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Ah, sounds good! :hattip:

Though it won't eliminate M clunk. That's a "feature" of the car.

cmstrilchuk Thu, Dec-14-2017 07:30:07 PM

Re: Adjusting Diff backlash (eliminate M clunk)
 
CV, guibo and U-joints are good?

New driveshaft 'cured' my clunk.

TheCoder Thu, Dec-14-2017 07:43:15 PM

Re: Adjusting Diff backlash (eliminate M clunk)
 
Quote:

Originally Posted by cmstrilchuk (Post 1067760275)
CV, guibo and U-joints are good?

New driveshaft 'cured' my clunk.

Cv and U joints are fine. Guibo needs replacement , but it is not the cause because i held the diffs input flang, turned the output and observed a clunk.

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M3_Pilot Thu, Dec-14-2017 08:46:21 PM

Re: Adjusting Diff backlash (eliminate M clunk)
 
Hmm, I’ve never heard my car clunk before?

OneFastSicilian Thu, Dec-14-2017 08:49:06 PM

Re: Adjusting Diff backlash (eliminate M clunk)
 
I have an 05, i purchased it from an older lady who bought the car because she wnted something fun to drive and never went over 5k rpms.. so she says.... but I dont have any clunks at all.. I think there's more to it.. i wouldn't mess with the backlash but if you're in there.. do some gears!

Fhcrubarb Thu, Dec-14-2017 09:22:10 PM

Re: Adjusting Diff backlash (eliminate M clunk)
 
How likely is it that our diffs completely fail and self destruct, especially during track conditions? My diff has been clunking and probably feels as yours does OP the feeling of slop in the diff (I just did vince bar, poly diff and subframe bushings etc. so everything is pretty well locked down). I'm contemplating having it rebuilt and or just leaving it. It's a track only car.

MOTRSPRT Thu, Dec-14-2017 10:57:58 PM

Re: Adjusting Diff backlash (eliminate M clunk)
 
The clunk in my car was HORRIBLE. My wife stopped driving it altogether. I relearned how to shift to avoid the clunk. I finally took it to my Indy shop to replace the rear diff bushings. Iíve already replaced the GUIBO and CSB when I installed adjustable camber arms. When my Indy shop got it in the air they found the bushings were in pristine shape but noticed the one bolt which goes
In from passenger side going across towards driver side had backed out. After they tightened it down 95% of the clunk went away.
Something to check I guess.


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