> I've recently had my front drive shaft replaced on my 87 syncro westy.
Since
> then I notice a significant vibration starting at around 42 mph and
> gradually decreasing around 50 or so. My mechanic assures me that the
drive
> shaft was balanced.  He suggested that it might be my tires so I had that
> checked and they were not the problem.

If it is not a new VW OEM drive shaft, it is most likely the drive shaft
being out of balance... the archives are full of experiences of being unable
to rebuild the driveshafts without getting a vibration... even after
balancing! The most successful rebuilds seem to be the ones that remove the
rubber boot and rebuild the shaft without a rubber boot....

Good Luck,
Bill