Transmission rumbling sound- 1988 300E
 

I can hear a rumbling sound coming from the right rear of the car when the load on engine is reduced i.e. when going down hill and overall there's seems to be more vibration will driving, similiar to type of vibration that you get at idle when the motor mounts are busted. The vibration doesn't occurr at idle, only when the gas is backed off when the car is at speed. Any ideas?

New rear axles solved the same problem on our 190e.

check the driveshaft flex discs, center support mount (remove exhaust heat shield), rear axles. I had more vibration when going downhill with foot off gas and suspension work fixed that for me - it was either the subframe mounts and/or shocks - I did both at the same time because of time contraints.