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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 Tue, Jul-11-2017, 03:29:10 AM   #11
dustins
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Default Re: Chasing E46 M3 never ending thud while shifting

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Originally Posted by bigjae1976 View Post
The M variable diff has unequal output shafts so the theory is the diff will develop a clunk over time. Its not an issue.
Yea, both diffs have slop between the output shafts which sucks, considering an e36 LSD with 200k KMS is usually tight as can be.

I'm sorta considering buying a new fresh build diff with upgraded LSD from Turner or Diffsonline
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Old Tue, Jul-11-2017, 03:46:24 AM   #12
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Default Re: Chasing E46 M3 never ending thud while shifting

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Originally Posted by dustins View Post
Yea, both diffs have slop between the output shafts which sucks, considering an e36 LSD with 200k KMS is usually tight as can be.

I'm sorta considering buying a new fresh build diff with upgraded LSD from Turner or Diffsonline
Most LSD's have some noises to them. Especially the ZF clutch pack type LSDs. So if a clunk is annoying, clutch chatter will be just as bad. You can add FM but then that changes the lock up and defeats the purpose of the LSD.

If you want silent, get an open 210mm diff unit from an earlier V8 5 or 7 series.
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Old Tue, Jul-11-2017, 04:13:06 AM   #13
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Default Re: Chasing E46 M3 never ending thud while shifting

Do you have an adjustable clutch pedal bump stop? If so, might be preventing full clutch disengagement.
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Old Tue, Jul-11-2017, 05:16:27 AM   #14
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Default Re: Chasing E46 M3 never ending thud while shifting

I recently built a new race car out of a stock smg car. I was shocked to find out that 2 of the 4 transmission mount had cracked and were completely torn off the frame.

I drove the car for a few days, before tarring it apart, and it M clunked so hard each shifts.

Maybe this could lead you in the right direction...
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Old Tue, Jul-11-2017, 02:54:43 PM   #15
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Default Re: Chasing E46 M3 never ending thud while shifting

When is the last time your motor or transmission mounts were looked at or replaced. It sounds like one of the two to me.

Also, I'm surprised you went to poly diff mounts since NVH seems to be a concern to you. Stiff diff and transmission mounts are the biggest contributors to NVH, even more so than engine mounts.
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Old Tue, Jul-11-2017, 03:04:23 PM   #16
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Default Re: Chasing E46 M3 never ending thud while shifting

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Originally Posted by dustins View Post
Sorry I was referring to the first reply claiming its just M-clunk.


I've never tried the e brake thing, but since I am able to reproduce this sound by rolling 60km/h holding the clutch to the floor and shifting between 3rd and 4th back and forth I believe the thud is transmission/diff related (internals).
I must have glossed over this last night, but with the clutch fully depressed you're having a thud each time you move from 3-4 and 4-3?
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Old Tue, Jul-11-2017, 03:07:36 PM   #17
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Default Re: Chasing E46 M3 never ending thud while shifting

I replaced my motor mounts, trans mounts, trans guibo, and CSB, and I still have the clunk. I plan to replace all the bushings in the rear, but I think it's just play in the driveshaft/differential rotating assembly. Putting the transmission into gear causes the output shaft to rotate slightly and takes up the "slack". You can watch the driveshaft spin when you put the car into gear on jackstands. This is my theory anyway.
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Old Tue, Jul-11-2017, 03:22:29 PM   #18
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Default Re: Chasing E46 M3 never ending thud while shifting

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I replaced my motor mounts, trans mounts, trans guibo, and CSB, and I still have the clunk. I plan to replace all the bushings in the rear, but I think it's just play in the driveshaft/differential rotating assembly. Putting the transmission into gear causes the output shaft to rotate slightly and takes up the "slack". You can watch the driveshaft spin when you put the car into gear on jackstands. This is my theory anyway.
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Old Tue, Jul-11-2017, 03:39:40 PM   #19
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Default Re: Chasing E46 M3 never ending thud while shifting

'M-Clunk' from slop inside the diff has pretty much been beaten to death...
There's a second possibility for driveline slop, and that's the dual mass flywheel.
Doesn't sound like that's the case here, if you can see the driveshaft move with the wheels stationary.
There are other options for a replacement LSD assy besides stock and retrofitting to the earlier (and slop free...) clutch pack LSD. OS Giken and Quaife probably make something, and there's also 'Wavetrac', which I'd never heard of before...
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Old Tue, Jul-11-2017, 03:40:14 PM   #20
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Default Re: Chasing E46 M3 never ending thud while shifting

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You think this explains the thud in all occasions? I'm not so sure I agree
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Discussing Chasing E46 M3 never ending thud while shifting 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)