Jill,

What maybe happening to your trans is that the clutch hub for 3rd and 4th gear
was known for cracking.   When they crack they will shift around on the shaft
which can lead to it popping out of 4th gear.   I will gladly give you more
information
if you want but in a nutshell this is more than likely what is causing your
problem there.

As far as 2nd gear goes I suspect that these are the old style syncro rings.
These
rings were not the newer 'moly' coated style and can cause difficult gear
engagement.
Also, since you stated that a GM and not a VW dealer did the orginal rebuild
they may
not have installed the correct gear oil.   The biggest mistake that people
make is to use
a petroleum based non-GL4 product.   Your trans should only be filled with
either the factory
G50 synthetic or either Redline or Amsoil GL4.  The other gear oil weights
contain sulphur
compounds that can react with the brass syncros and cause premature wear.

Bottom line is that if your trans is popping out of 4th and is difficult to
shift into
2nd then it will have to come out and be disassembled/inspected and the
correct
new parts installed.

Keep in mind that I am diagnosising by the internet and there is a slim chance
that
something else could be causing your problem.  (But I doubt it)

Todd Hill
VolksWerks Transaxles
Olympia, WA