Here's what not to do to your transmission:
http://www.251.org/images/rebuild/Transmission/

This transmission was original with apx. 175k miles, 1500 of which were
towing a 2000+ lb bus.  I replaced the CVs earlier this week and decided to
change the gear oil as well.  The CV replacement went well, all of the CVs
were original, all of them were pitted, but not severely.  The left inner CV
joint was in bad shape due to a cap that had come out of the transmission
final drive and let gear oil into the joint.  When I drained the
transmission the redline MTL came out silver with pebble sized chunks of
ring gear.  So it was rebuild time, I am not rebuilding the transmission,
I'm having it done at my local VW shop.  The transmission seemed to run ok,
it was loud, a constant whine and seemed a little rough. (which is one of
the reasons why I decided to replace the CVs)  But not too bad considering
the condition of the ring gear, not pictured is the pinion which had the
teeth worn to very (very) sharp points, guess how we found that out...

The front transmission mount was very collapsed, there was apx. 1/4" gap
between the rubber and the metal sleeve.  The symptoms I contribute to this
were occasional bucking in reverse and 1st and what felt like clutch
stutter.  Although the clutch problem could be unrelated it is likely that
the mount is the cause, the clutch is new (50k miles/ 2 years old) as is the
rest of the motor including the pressure plate (resurfaced).

The rebuild is in progress, I'll keep you posted.

dave
www.251.org
87 Vanagon
61 bus