Q). Have you ever had any work done on the rear diff or center drive shaft? Has the driveshaft ever been taken off? Or the flex disc(Guibo)?
Q). Has the vibration always been there? Or has it started all of a sudden?
A1: I don't know...I bought the car used with 60k km on March...but it was fine and has always been till now.
A2: The vibration started after the last service done by them 2000 km ago with also new OEM pads. (I think they just mess up something!)
Anyway...the dealer is still saying me that there is no problem with my diff (and they should be right) but I already order the +FM for the diff and some trans oil just in case...the shop that take care of my track car is going to do all the oil change...they already changed the silent blocks and did a really nice job even if they have never work on a E93 M3 before, but at least they have 30 years of racing experience, grease and steel knowledge!
Thanks for the advice!