"Secondly the vibration is still there when the car is "rolling" with tranny in neutral... "

The gearbox disconnects the engine from the shaft not the shaft from the back wheels!!

When you are rolling the transmission shaft is rolling as well.

YES the gearbox is different from a 93 to 95 S500, but the shafts are exactly identical.

The trans shaft only last in decent shape for 200.000 km, and if you run with the engine mounts dead it will go bad much sooner.

You can forget about the balance, with the W140 power steering any minor unbalance is felt in the steering wheel. That’s why they always have a slightly steering shimming.

__________________
________________
Folgado
S 500