>start spinning.  This situation would be *greatly* improved if it had a
>locking differential (can you get these for a non-synchro?).
>
Maybe, try Weddle Engineering in California somewhere.  He fits 'LockRite'
locking diffs into Syncros (up front and rear I think)  If anyone can help
you on this he can.  $300 for the unit, plus installation!,  ie. send him
your trans!  These lockers are alway 'on', no switch, they engage/disengage
when needed.  Heard they clunk and kick a bit.

        As Tom Johnson suggested, using your parking brake will help.  A
regular 'open' diff transmits no more power than what the spinning wheel
carries, ie. zero, but if you can brake the spinning wheel then you will get
power to the opposite (gripping) wheel equal to the braking force applied.
Hummer drivers use this even with limited slip diffs (Torsen type), called
'brake modulation' easiest on vehicles with auto trans, two feet in at once
until you are rolling then let off the brakes.  Or get a split emergency
brake set-up like dune buggies and really have fun.

        For the Jetta you can get a Quaife ltd. slip, $900 I think, hard
install, not DIY I read.

Tim, 

Who has recently discovered doing E brake turns in a Syncro doesn't work,
major bummer. Working on power turns in the snow, hard to get the rear to
break loose, front just pulls you back in line.  Wah, most of my winter
tricks are gone, well, not really :)