Rear Axle Vibration?
 

My 1977 W123 car has new flex discs (bolts are tight), centre bearing & support, driveshaft alignment bearings, differential support, motor & tranny mounts, recently balanced driveshaft.

I still have vibrations from 40 mph through 60 mph and at 40 the vibration is more pronounced when cornering - more to the left than to the right.

The axle cans have no leaks, but they are the originals (239K miles). I now think they may be the culprit.

Does anyone agree?

When fitting the new driveline parts - was this done with the weight of the car on or off of the wheels?

Weight on the front wheels and weight off the rear wheels.

I have done this about 5 times now. One time I left the centre carrier bearing support slightly loose, drove the car a little, and then tightened it but with the rear wheels off the ground again.

...and with the prop shaft nut loose too I assume?

And checked for exhaust hanging obvious-ness too I guess...

...and the tyres and wheel weights are all OK? Swapped front wheels with back...

What about the sub-frame mounts. There's a front and rear on both sides of the rear suspension. The rubber dries out and cracks causing play, resulting in rear wheel vibration.

Everything mentioned has been covered with the exception of renewing the sub-frame mounts, although it seems to me that the problem has to be with something that turns as it occurs at certain speeds only.