Rumble/Drone from driveshaft/diff
I just swapped out my automatic for a standard 5spd, and all is working perfectly, except from roughly 50-70kph (speedo is insanely optimistic so i'm guessing here... it's basically from 3rd at 2500ish and up rpm to a low 4th gear) there is a loud low pitch drone/rumble coming from the middle/rear of the car. It doesn't shake the car much at all, just noisy.
Now the diff is exactly the same as before, so i'm not sure if it could be that.
Schwartz '89 325i
M50 finally done! Loving life.