[E46/M3orBust]

So I've seen on a lot of online forums where people address this issue. They always assume it is the subframe but I had this exact same problem and my subframe was reinforced less than 10,000 miles ago. It felt like my entire rear subframe was moving each time I accelerated or reversed. So I put it up on a lift and had someone accelerate and found the issue to be the Differential mounting bushings were very worn and the mounting hardware inside the bushings was moving hitting either the top or bottom of the mounting sleeve. If you have this issue get the car up on jacks and check those bushings under acceleration. I didn't have the tools to press these bushings out so I went ahead and just bought a new diff cover with brand new bushings already on. Hope this can help someone

[jp1984]

Thanks! As all of our cars get to being 20 years old, this information is helpful. good job!

[NealfromNZ]

The diff bolts on the earlier M3s can also cause play and knocking sound. Later diff bolts help to remove the play.

http://www.psdesignsglobal.com/_shop...f-mount-bolts/