You could pull up on the handbrake, while holding in the lock button and modulate pressure to stop the free-spinning wheel and send some of the drive torque to the other one.
  It's an old off-roading trick, and if you had cutting brakes (2 separate non-locking levers), like some rails or buggies have, you'd be able to do this job even easier.
  Try it some time when you're stuck; it really works!

Mike B.
  ----- Original Message ----- 
  From: David Beierl 
  To: vanagon@GERRY.VANAGON.COM 
  Sent: Sunday, April 12, 2009 7:48 PM
  Subject: Re: Only ONE drive wheel?

  At 08:28 PM 4/12/2009, Brian Doss wrote:
  >I have an '88 GL with a manual transmission. I got it stuck backing
  >into an uneven driveway yesterday. Just so happened that I was in a
  >saddle on a hillside, with just enough torsion on the bus to lift
  >the left rear wheel off the ground - and presto - no go. The left
  >wheel spun happily in forward or reverse. What I can't understand is
  >that I thought the right wheel was driven as well - why did it not
  >receive any power? Does this mean something is wrong with my transmission?

  You're fine.  The way a regular differential is built, it will drive
  two wheels at different speeds to let you go around corners and such;
  but both wheels have to have traction.  If one loses traction, it
  will cheerfully spin at double speed while the other wheel stands
  still.  OTOH if you bolted (or braked) that one so it couldn't turn
  then the wheel with traction will be back in the business.

  There are "limited-slip" differentials which will prevent you getting
  all the power to the wheel with no traction; and there are
  differential locks that effectively turn the differential into a
  solid axle -- great for traction but horrible for turning.

    --
  David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
  '89 Po' White Star "Scamp"