89 trooper transmission problems

Anyone out there familiar with the auto tranny on the 4 cyl 2.6L? My 89 trooper won't shift past second (or maybe third), and I'm wondering if this is a common problem with an easier fix than a rebuild/replace or what.

The rebuild looks like a $2000 fix on a car that's worth half that. Any suggestions? Thanks.

Help--haven't heard anything and repair shops want "to get it on a lift" (start the lubing and bending over) before they vebnture any guess at all. If it would upshift, I could go ahead and take it in, but I'd rather have some idea of what others think before I do that. Thanks!