'87 740 turbo

When driving I get a low frequency hum in the cabin (no snow tires), as though the motor mounts are bad and the noise is being transmitted through the frame. I know what this is like as it happend to me before. Checked the motor mounts and they look okay.

The noise is even lower when the car is loaded in the rear (full of people).

I already know that I need new springs, as the car sags slightly on the left rear.

Could this be the tranny mount?

I also notice when driving over bumps, the stick (manual tranny) moves up and down slighty. There is no knocking when this happens. Just seems as though the tranny mount is spongy.

Is it worth replacing the tranny mount? or wait until I change the springs and see how it is then?

Cheers

When the noise began had you recently done anything to either of the fuel filters/pumps? I replaced transmision, mounts and fuel pump and from then on had this noise(I know, bad to do multiple things but mechanic had a free weekend).

hi
check the center support bearing and rubber (center line drive shaft) if this is worn it makes humming noises at take off and accel more noise when heavy
good luck
Matthieu