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Mechanic says my diff needs to be replaced

572 views 1 reply 2 participants last post by  lszlszx 
#1 ·
My car is experiencing an excessive clunk when shifting the load at low rpms, it is particularly noticeable when shifting out of reverse. I know this is consistent with the typical M3 clunk, but this is much worse than any I've heard before.

Took it to the mechanic today to identify the source. He put it on the lift and we inspected it together. Initially the mechanic noted excessive play in the driveshaft, but his tech claimed this was normal. We worked our way back to the diff and it appears the right output shaft, at the interface with the diff, moves much more than the left output shaft. I believe the right is supposed to have a little more play, though my left doesn't move and the right moves fairly easily.

Per Realoem I don't see a bearing where the output shaft connects to the diff. No leaking, squealing or any other evidence. Mechanic wants to replace the diff.

Should I remove the output shaft and inspect the spline? If the diff needs to be replaced what is the level of DIY difficulty? I've done many DIY projects including installation of a turbotoy vanos hub. Can I DIY without a lift?
 
#2 ·
It's not a bearing, or play at the spline, but gear lash inside the differential.
I had an E36 M3 that had a clunk at the differential and was considered a fairly common problem, so I just put up with it.

Not sure what the mechanic meant by excessive play in the driveshaft is normal.

If the clunk is indeed the right side of the diff, it would be easy to hear it as a helper shifts the tranny back and forth between D and R.

You can easily replace the differential if you have mechanical experience, a driveway and basic tools.
 
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