After my 1990 Vanagon Multivan sat unused for about a year because of an automatic transmission failure, I finally found someone in my area with a used auto tranny from an '86 Westy for sale.  The auto shop at the high school where I teach installed it for me under the guidance of the auto shop instructor, who is a former VW mechanic.

Sadly, it's still not usable. Now, when I put it in reverse, it feels as if I'm trying to back over an enormous speed bump.  It backs up very slightly, but stops, seemingly as if it's trying to back over something far too steep.  Yet, if I put it in reverse and don't apply pressure on the gas pedal, it will roll backward slowly but freely.

The former owner of the transmission, who has since moved out of the area (meaning that I'm on my own with this problem), seemed like an honest young man who claimed that it came from a Vanagon that he owned and that it had worked fine when he removed it.

Could there be another explanation other than the transmission not working correctly when I purchased it?  What would be a next step in diagnosing the problem?

Thanks in advance for any help and suggestions.

Ken
Western Washington