My 1990 Dynasty with a 3.3 auto. Started shifting wrong ,It was driving just great ,Then one morning it would only stay in first gear & not shift up ,reverse still works ,it shifts kinda hard into gear ,the trans does not have that many miles on it since a rebuild.
Someone told me it was the speed sensors? I felt like there was something wrong with the trans.? I don't know. any help would be appreciated. Thanks ...James.

 

How long has it been since you have had the trans serviced? (new filter, fluid, flushed, and bands adjusted)