It has been a number of months since we last had a viscous coupling
 out of a syncro's front drive. It was removed in order to have it
 refilled with new fluid. It was to be refilled by Steyr Daimler Puch
 in Austria. My friend who happens to be an Austria citizen, was
 doing some work for them at the time and i think they were going to do 
 this service for him as a favor. The Viscous was removes here in the  USA
 and on one of his trips home, he took it with them. To make a long story
 short, instead of refilling it, they just gave him a new unit.

 From seeing the Viscous Couplings first hand, i will not say that
  it is impossible to refill, but i think that it would be difficult.
  Generally the reason for viscous failure is contamination of the 
  silicone fluid which is supposed to be permanently sealed, with the
  surrounding gear oil which is in the front drive housing.

  This contamination destroys the viscous coupling's ability to transmit
  torque through itself. Steyr as far a i know modified the Viscous
  couplings to counteract this problem, by pressurizing the viscous
  slightly. This is information which i cannot prove, but i cam
  e from a pretty good source. This modification was made some where
  along the production, but i'll have to try to find out some dates,
  etc...

  The Viscous however is clearly marked,  "SDP - AUSTRIA"
  and to my knowledge is made by them at their factory.
  i will try to get some specific info as to the refilling and
  if it is possible from SDP, but it will take a few days,

patrick