At least i think it is a tranny issue.  Here is the story.
A real 'risen from the dead' bus story.

82 passenger van..............Stood up for about 3 years.  i put in used
engine i had (120+ lbs compression on all cylinders....I pumped the lifters,
put new seals, etc.......endplay good, so did not split the case ) it is
timed correctly and valves are adjusted fine.  I have drained and replaced
the tranny fluid, and cleaned the screen................did not have a
replacement at the time. Screen had a little brass in it but nothing major.
It runs pretty good at idle, and the tranny is not slipping or
anything............when i go from a stop, it drives with normal vanagon
power until 15mph, and then it shifts to second, where it is real
slow..........the rpms are sounding normal, not like anything is slipping,
but REAL slow up until about 35 mph, where it starts to pick up a little
better.  BUT then at around 40 mph, it shifts to 3rd.  same
story..............slow to 60 mph, even the slightest hill slows the van
down some.  Top speed I was able to get out of it was about 65 mph, on a
flat.

Now I have driven air-cooled automatics before, and they have had more power
than this.............

On the good side of things.The more we seem to drive it, the better it seems
to run.......................before we drained and swapped fluids the tranny
did terrible..............

Adam P
81  Westy "The Brick "
70 Single Cab "Whitey"
74 Beetle "Ol Yeller"
73 Transporter (STILL at paint shop)
1988 Vanagon Wolfsburg
1976 Transporter (New CA bus)
75 Campmobile "for sale'
Used Vanagon Parts for sale (mostly aircooled)