Lots of clunking that sounds like it's coming from the differential.

[DreamTime]

Originally Posted by pbonsalb

Are you sure there is no play in your rear suspension bushings? I could easily twist my rear toe arms back and forth with my bare hands until they hit metal, Replaced them and can barely twist them at all now. I replaced my rear subframe bushings with 75D poly and the rear end is much more planted now -- no wiggling or jiggling. At the same time, I did the diff bushings in 95A so it is not moving as much. The rear diff bushing is a 1 inch aluminum piece with 1/4 inch of foam around it so there is definitely some play in it.

I will say that after tightening up my rear end, I hear a little diff whine from 65-75 mph from the stiffer diff bushings and actually a little more drivetrain noise of the clunking type from the driveshaft and maybe axles. But mine is not bad and does not bother me.

It is possible your problem is inside of your differential -- I don't know. I had not read of internal diff problems with these cars although I have read that the visco limited slip may wear out over time. I recently drove a 135i with an aftermarket helical limited slip and that diff definitely clunked noticeably.

I know I have a lot of suspension work to do this winter, just trying to wrap my head around where to start. Could that maybe contribute to a noisier then usual rear axle? I mean, I can't say with 100% certainty that the clunking was coming specifically from the diff, although many super qualified people told me it was. When I changed the fluid I did notice the old fluid had a distinct bright silvery color to it (it had been about 30000 miles since it had been changed) and it looked like there may be a tiny leak at the front seal, although there are never any signs of fluids dripping on my garage floor. Maybe I am over thinking it, not sure... Like I said, I have had several professionals look at it and they don't think there's a problem. Just want to be sure I guess

[pbonsalb]

I don't know. I have clunking also and it seems others do as well. But it may be that nothing is wrong and that clunking is ok for these cars. I don't think my drivetrain noises have gotten any worse in the past 7 years. I do think that changing to stiffer bushings amplified the noise a little but to me the stiffer bushings are worthwhile. I would not rush out to rebuild a diff unless I was experiencing a performance problem.

[RomanK]

Originally Posted by pbonsalb

I don't know. I have clunking also and it seems others do as well. But it may be that nothing is wrong and that clunking is ok for these cars. I don't think my drivetrain noises have gotten any worse in the past 7 years. I do think that changing to stiffer bushings amplified the noise a little but to me the stiffer bushings are worthwhile. I would not rush out to rebuild a diff unless I was experiencing a performance problem.

Perfomance is normal for me in my case. The locking works good and nothing noises.

But I don't need to feel the kick to my ass when I open a throttle on high speed... this is most what I am worried. Even if it is normal... That is bad.

I drove the same car of my friend and nothing kicks there... but my car kicks me... And I in a fury!!

[DreamTime]

Originally Posted by pbonsalb

I don't know. I have clunking also and it seems others do as well. But it may be that nothing is wrong and that clunking is ok for these cars. I don't think my drivetrain noises have gotten any worse in the past 7 years. I do think that changing to stiffer bushings amplified the noise a little but to me the stiffer bushings are worthwhile. I would not rush out to rebuild a diff unless I was experiencing a performance problem.

There is definitely no loss in performance, as far as I can tell. I think I just need to listen to everyone and accept the clunky rear axle as normal. I love this car so overlooking something that bothered me at first is no big deal, as long as I am confident there is nothing wrong. I do check on my diff every time my car is on a lift, just to make sure everything looks okay (ie: the little bit of seeping I noticed at the front seal), and I plan on changing the fluid again at the next 30000 mile mark. So far so good I guess

Thanks! No more differential questions for me at this time.

[JetBlack_M3]

Originally Posted by RomanK

Who knows, this is normal or not?

Mine makes that same clunk sound

[divadp17]

When I bought my 08 m3 with 65K miles I didn't notice any clunking noise from the rear diff but after i upgraded to solid rear sub bushings and replacing all my arms with spl(spherical joint) I have noticed the same type of clunking noise from the diff area when accelerating from a stop. Since everything in the rear suspension are solid except for the diff bushings I can only assume that all the load is transferring to the diff bushings causing it to make that noise. I haven't check if my diff bushings have gone bad yet but I do plan on upgrading them to poly and when I do I will keep you guys updated whether or not that fixed the clunking issue.

[noremaC]

Spencer Burke recently came out with a well documented video with some good info. Based on the video, it's the center support bearing/driveshaft hitting the heat shield because the bearing is failing, causing the driveshaft to sag and hit the metal heat shield below (or close enough to this, still the basis of causing noise).

In my personal experience, this started happening a couple weeks ago (70k miles, E90). I started noticing a higher pitch 'clink' when taking off in 1st gear (happens when car is cold or fully warm), only from a stop to low speeds and goes away after the immediate sound occurs. The best I can describe the sound is like an empty glass bottle rolling around under my seat and hitting the metal seat rails (clink-ing sound). The sound seems like it's coming from where the center support bearing is.