Strange shifting on automatic Toyota Corolla

My 94 Toyota Corolla has about 190,000 miles on it and lately it has had a hard time shifting between 20-30mph. It finally does reach it and does not have trouble shifting at any other speeds. This only happens in the heat of the afternoon (Never have this problem in the morning). Also, my O/D light has been flashing when this happens, or at least around the time it happens. Could these two problems be linked? I took it to my mechanic in the morning and he checked the transmission fluid and it seemed fine, he also had no problems driving around when he tested the car. He said my transmission is going and that I should make “long term” plans. Is there any hope? I have a year to go (or thats what us grad students always say) at school and I wanted to keep it until then.

Its likely that your only hope is that it keeps limping along well enough to get you around for another year. Don’t take any long trips.

If you really want to know what is going on you have to take it to an actual transmission shop. Most general mechanics know very little about automatic transmissions or how to diagnose them.

Yes, on the O/D light & shifting problem - that light is telling you that the computer sees a transmission problem. A transmission shop can pull the error codes and get a clue. When you find a transmission shop make sure it is a locally owned place rather than a national chain operation. You could have something as simple as a loose wire.

That said, its going on 20 years old and has high mileage so I wouldn’t expect any miracles out of anyone. This is most likely the beginning of the end no matter what. What have you had done with the car in terms of transmission service?