Check out the rear!
Have the rear end differential checked out as they are prone to pinion bearing & seal failure.
Listen for a humming in the rear(as a function of road speed). Mine used to sound like a fully laden B-17.
A factory rebuilt can be expensive.
'84 190E 2.3
'83 Porsche 944 (track car)
'84 Porsche 944 (parts car)
85.5 Porsche 944 (sled)