I have the same problem in my 86 Syncro Eric.  My assumption (untested)  was 
an tire out of balance.  ??

paul

 ----------
>From: vanagon
To: Multiple recipients of list
Subject: Syncro Vibration problem
Date: Thursday, November 07, 1996 12:03PM

   Well I think I have hit the last big problem with this Syncro.
   At about 45 MPH the van vibrates. At 60 MPH, smooths out again.
   Sometime ago I had a car with a bent drive shaft, it feels
   the same. With the car, you could see the shaft as it turned,
   that it was bent. In the syncro I can't find any sign of a
   driveshaft problem. Has anyone had a vibration Like this?
   My nexted guess is the front axle. If someone on the list has
   had a problem like this I would like to hear from them.

                 Eric Zeno   <emz@nauticom.net>
                 86 Syncronizer
                 86 GL  For Sale (Pgh. PA)
                 72 240Z    1936 Chrysler