I have some issues with my 2000 LMS M5 with 73.000 km that I recently purchased. When I drive so there is pressure on the drivetrain (and in normal Finnish roadspeed 80+ km/h when there is little other noice e.g from engine) there is a clear high "pitching" noice from the rear "axle" (?). Immediately if I let up the gas it stops. Furthermore if I gas quickly and let it up, there is a clear "gap" that you feel in the drivetrain. According to a mechanic it is not from the rubber bushings but from the "rear axle". Some part(s) are apparently worn so the settings in the "rear axle" are screwed up and hence the noice and "gap". Any ideas/experience what it is and what can be done?