I got a 89 GXE with 170,000 on it. You know when you start the car and it does a system check all the lights on the dashboard light up? Well I noticed that if my lights don't light up for the comfort and sport indicator for the transmission the transmission will drive like its a cvt more or less and not go into 4th gear (overdrive). It usually last just the first couple miles of driving then will shift perfectly fine or wait till it gets to operating temperature. But if the lights do light up brieftly when I start it shifts normally like its supposed to. It doesn't do it all the time and I don't think it matters how cold or hot the engine is or if I've been driving around all day or anything like that. It just does it when it feels like it. Anyway. Do you guys/girls have any suggestions as to why it does this or can point me in the right direction.

 

try replacing the switch....