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Old Tue, Jul-11-2017, 11:00:44 PM   #25
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Default Re: Chasing E46 M3 never ending thud while shifting

Sorry I can't quote and reply to everyone;

But again, its not "M-Clunk" I know what this sound is and how you are able to avoid the car producing it by manipulation.

I went with poly diff bushings because of a sale on ECS, during the time of ordering the Turner kit among other items. No noticeable noise difference with the poly diff bushings as I went with OEM subframe, combine the 2 together with poly and yes I get that there will be an increase. Thud is no harder for softer than prior to all of my work, only thing I noticed is slight diff whine at highway speeds. (Only if all the windows are up and blower is off).

Obviously my issue is in the diff, or transmission (DMF maybe even) I am just trying to narrow it down. Again going back to what I've said a couple times is that cursing 60-80km/h with the clutch fully depressed (pushed to the floor) I can shift back and forth from 3-4 4-3 and can reproduce the thud sound. I at one point thought that maybe the clutch wasn't fully disengaging and maybe it still isn't, but I've bleed it a couple times and removed the CDV.

Other things I notice I can do to avoid the thud is shift slow, I mean push the clutch in wait a full second or 2 without touching the shifter and then change the gear. I also notice it does not happen quite as often when I fully lift my foot off the gas pedal while switching gears, hard to get into the habbit of doing that as in all my other 4 bmw's I've owned (mind you none of them M3s) I was always able to rest my foot on gas though still letting up on the throttle while shifting (Just dont rest your foot on the clutch right ha )

No clutch stop in the car either.

Part of me thinks maybe the synchros are shot maybe, and that quick shifting while everything in the tranny is still moving is causing the thud. As I mentioned before, its super notchy down low (under 4k rpm through 1-2-3) but doesn't grind any gears when power shifting at 8k rpm.

I've spend countless hours reading threads from all the BMW forums and it always ends up talking about M-clunk and I understand what that is but I'm certain this is something deeper. It only bothers me anyways, car still drives fine, I still slide corners and rip on straights

Maybe this coming winter I'll just order an upgraded diff and try to find a low mileage Getrag 420g and see how that does. I thought about trying to find a 540i 6MT transmission that hasn't been abused and stealing the Getrag from it and swapping my bell housing to fit it into my M.
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