> Also, if you ever disassemble the driveshaft, be sure to put it back
> together with the U-Joints in correct phase.

O.K. Tom, I'll bite, how do you determine the correct phase of a U-joint?

> I have never seen a Syncro dirveshaft. Can you describe the mechanical
> configuration?

The main drive shaft on a syncro (not the axles) is similar in length to a
conventional shaft on a domestic car.  One end has a welded on yoke with a
conventional U-joint and a flange that bolts to the front differential.  The
tranny end is a different beast. Starting at the tranny, there is the same
flange as on the front end of the shaft.  Into that flange is the U-joint
and another flange that bolts to a concentric rubber donut.  The donut
(re-inforced) then bolts to four bosses that are part of the welded end of
the shaft.  My assumption was that the donut carried all of the force
similar to what you would see on a steering shaft connection.  That was
partially correct, as the torque is carried by it, but what you don't see is
that there is an extended shaft (~6") that goes into the welded end of the
shaft that ensures alignment of the flange assembly and the shaft.  The
"flange shaft" is necked in the middle and had two support surfaces, one at
the base and one at the end.  They ride in bronze bearings and prevent
deflection of the yoke due to the flex at the donut.  The end of the shaft
is where I saw the wear marks that I believe are the culprit.
Sorry to all of the non-syncro owners if the description is boring to you.
I have just seen too many requests as to why they have a vibration around 50
mph that they couldn't explain.  Hope this helps.
Mark Rokus
'87 GL Syncro Westy
'87 GL Syncro
'86 Syncro (hanger Queen)
'81 Westy Aircooled
'82 Rabbit Diesel