>not a differential.  A DIFFERENTIAL PROVIDES SLIP UNDER LOAD (ie cornering)
>A VISCOUS COUPLING LOCKS UP UNDER LOAD AND provides SLIP under NORMAL
>CONDITIONS.  The two are completely opposite.

yup, but the VC in a Syncro is acting as a (centre) differential to keep the
driveshaft from winding up due to different front/rear axle speeds. I can
see how a permanently sticky fluid would work just fine as a coupling and
diff.  It will always transmit power, up to its designed capacity, but if
the coupling was being stalled by turning radius effect then it would have
enough give to act as a differential.  Thus the diff function becomes an
'overload' condition, while normally power is transmitted.  We are all
assuming that the VC doesn't transmit any power to front wheels when going
straight ahead, and that is true, regardless of fluid viscosity, since no
shear = no power transmission.  So a very thick OR very thin fluid would be
fine. A thick fluid would transmit power the minute it became sheared, like
cornering/wheelspin, while the thin fluid never would. 

>How often have any of you Syncro owners had to change a VC?  Is it often
>enough that it makes it not worthwhile owning one?  I am currently looking
>at an 86 Syncro that I can probably get for about $3500 (canadian), but 
not often, but enough have gone to scare hell out of me. At $2800 dealer,
$1400 aftermarket, any form of insurance is worth checking on.  They fail
from overheating and/or from contamination.  Low oil in front diff means
thay can't dump their heat out properly and they die.  Silt/water in front
diff means extra effort pushing the front axle, and they again heat/die.  Or
they may leak!

>think that one of our european listees could probably find some. . . At
>over $3000 a piece, a couple of us could get together and pay for a nice

the couplings are well over $1K in Europe.  Worth parting out a Syncro just
to get a spare coupling.  Where'd you say you saw that $3500 Syncro anyhow?
;>  Tim