After I had the M Performance LSD installed I was getting a thumping/rumpling noise from the back of my car every time I left a stop (see this link for the noise
). I thought the rumpling was the normal break-in noise everyone on this forum talks about. After 2K miles I took the car into the dealership for some engine warranty work, while it was at the dealership, the BMW technician told me my Drive shaft carrier bearing was bad. The dealership ordered a new complete driveshaft ($1933) and now the noise is completely gone.
After reading many BMW forums I discovered when you install a new differential in a BMW it is really easy for the carrier bearing to be installed up-side down. (see
https://www.e90post.com/forums/showthread.php?t=621437 ). I have no idea if the person who installed my LSD dropped the whole driveshaft when they installed the LSD or if they somehow just damage the driveshaft. In either case if you are getting that noise and rumpling sensation from the back, look at the Carrier bearing, and maybe try flipping it around. I hope my experience helps others.