In Reply to: Re: Diagnosis of rear end creak. (anyone agree?) posted by Pat Chiang on June 11, 2001 at 13:55:54:
I had the same noise in the diff when making tight turns in parking lots. It's the fluid in the diff. You need to get the right oil with the right friction coefficient.
My father was a Master Tech, and helped me fix it when he was alive. You need to goto a BMW Dealer. BMW contracted with Castrol to make a diff fluid specifically for BMW Diffs. It's call "X-??" something I can't remember the number. You have to request this special diff fluid, otherwise they will put the regular stuff in and that won't work. You can't get that stuff off the shelves. Try the redline and if the noise doesn't go away. Goto the Dealer and ask for the special diff fluid.
Pat '89 M3 - quite rear end :-)