[dirt57]

Hello! I wanted to ask about this problem regarding my Manual 335i X-Drive. Any ideas are welcome.

The problem is that when I am cruising in 4th-6th gears(also 3rd from some time now) with lower RPM and I accelerate hard I get this really bad vibration. Literally, the whole car is jumping. In lower gears, it's accelerating just fine. One thing I tried is rebuilding the front driveshaft(it had to be done cause it was in a bad condition) but nothing changed. Should I try rebuilding the rear one too? Might this be gearbox related? Would really appreciate your thoughts on this cause I really can't find the cause for months now(the car was like this when I got it)

P.S. I'm new here, sorry if I posted in the wrong forum.