The automatic on my 87 Westfalia suddenly and without any prior problem
stopped engaging.  If I accelerate hard, the van will red line remaining in
1st, and a slow build up to speed will cause an upshift to 3rd @ about
3000rpms.  I have changed the fluid faithfully every 20,000 miles for the
last 50K I have owned it.  The trans has 160K on it with no known rebuild.
Is is time for a rebuild, or is there an easy fix given the sudden nature of
the problem?
Thanks for your help, Finn Runyon