[John_T]

The center bearing is in the assembly around #7 in the second diagram. The center bearing itself isn't such a big deal, just getting to it is a job. I don't remember what it cost, was a few years ago. Don't want to get too set on that being the problem either.

Damage to the center bearing is generally due to hard shifts that slam the drive line, and while the center bearing is there to stabilize and brace the center of the drive shaft, it is also what takes the vector of the whacks.

You could buy or borrow a stethoscope and listen to different places while driving to determine where the sound is coming from and more of the character or the sound, but you are probably just as well off to take it to BMW and get them to diagnose it, since they are more experienced and better equipped.

[Wengy]

Thread bump. I'm looking for some other opinions. The center bearing is a good place for me to start, and I'll be picking up a proper jack and jack stands this week to put the car up. Anyone have other ideas what the sound may be, things for me to look at while I'm down there?

Need to do a few others things like pull the crummy CDV out as well.

[Procure]

John_T is referring to an issue outlined thread: http://www.m3forum.net/m3forum/showthread.php?t=273940

Is this the sound you're getting?

[Wengy]

Procure. No it's not the infamous M-clunk, I don't seem to have that issue. Certainly once in a long while I'll hear a clunk during a gear change, but it's not very often. My car's a 2001 with 38,000kms on it.

The sound I hear is not during the gear changes, but happens at low RPMs while in 2nd and 3rd gear, while the clutch is out and the gas is lightly engaged. It's a constant sound while the gas is engaged, it's very faint, a grinding or rattling sound, which only seems to be present when the car is coasting on straights or down a hill, not when the driveline or engine is under any real strain.

In that thread you linked a poster talks about: "flywheel-clutch-chatter(completely normal)". Anyone know what he's talking about, and what that chatter sounds like? I'm simply trying to determine if the sound I hear is a normal sound for the M3, or not normal. And if it's not normal, what the cause may be. Thanks.

[Wengy]

Still looking for more opinions on the sound I've posted up. Thanks

[John_T]

Does the sound remain more or less the same when you push in the clutch (disengage) while driving in the manner that you hear the sound?

If so, that confines the noise source to the drive line.

[Wengy]

Ok, I did as you suggested. The sound disappears when I push the clutch pedal down, and comes right back again when I re-engage the clutch. I kept my right foot on the gas and maintained the same 3000rpm throughout the test. Also, I tried to recreate the conditions while the car was at rest, but naturally in neutral there isn't any sound to recreate, and getting 3000rpm at a standstill is impossible without neutral.

[Wengy]

Ok, if the sound doesn't happen when the clutch is in, and I can't recreate it when the car is at a standstill, what does this tell me? What other likely things could be the source of the sound?

[Wengy]

Thread bump. I'm still looking for more feedback and opinions on the sound I'm hearing. Best guesses, divinations, conjecture, opinions, predictions, suppositions, and other forms of guesstimation are accepted.

[chasem3]

I cant hear the video here at work but since you mentioned it goes away when you depress the clutch pedal, it sounded familiar. I actually had the opposite issue. I have an SMG by the way but the concept/parts affected should be the same in a manual. In the beginning, I had a slight grinding sound when the car came to a stop with the engine on (like at a light), but would go away when i started moving again. SMG essentially depresses the clutch when you come to a stop and then reactivates it when you start moving. Eventually, the sound would come on all the time, clutch activated or not. I know my issue started out being the exact opposite of what you have, but I would think they are related.

In my case, it ended up being that my pressure plate came loose and was chewing up my clutch. It will get louder as time passes if this is the issue with yours and you dont get it taken care of. Since the clutch job is not a small one, you might as well change the clutch while you are in there. Thats what I did. I cant confirm this is your issue for sure of course, but this looks clutch/transmission related anyway. Like John_T said, we could diagnose this until we are blue in the face but taking it to an indy shop or BMW dealer is your best bet.

Best of luck.