I have a 97 grand prix GT w/ 150K miles that recently started acting up. Often the car starts out from a stop in a higher gear, especially in cold weather. Sometimes it makes a bit of a creaking noise when you put it in drive, which usually indicates that it got into a lower gear ok and you will not have the problem that trip. Also doesn't shift into higher gears at highway speed when the problem occurs. Usually if the car has reached running temp and been shut off for a significant amount of time, the problem won't occur. Had tranny fluid replaced recently. Fluid looks OK but may smell a bit hot. I noticed in the summer when the outside temp was above 80 or so, I wouldn't have any problems. Shifting manually, it gets into the right gear without a problem. Shifting is smooth otherwise. Any suggestions?

How about the screen filter? Was it replaced? Also, what tranny do you have? 4T60E or 4T65E. Check the SPID label on the back of the trunk lid. M13 - 4T60E. M15 is 4T65E. I suspect you have a older 4T60E. Those autotransaxles have a vacuum modulator which may affect shifting.

I don't believe they changed the filter. Only exchanged the fluid. And it is the older 4T60E, so either of those could be the problem. Any other possiblities? Thanks.

I don't believe they changed the filter. Only exchanged the fluid. And it is the older 4T60E, so either of those could be the problem. Any other possiblities? Thanks.

If you are unsure of when the screen filter was last replaced I would consider that first, especially with your mileage.

will do...Thanks again!

Transmission shop tells me that there is an electrical problem that is causing the trouble. Things are shutting down due to excessively high voltage output from the battery? Any experience with that sort of thing?

I would start looking at the alternator. Check the voltage at the battery while the cars running..

What are they saying is excessively high voltage? Is the battery/charging system light on? Typically you will have around 14.5 volts at the output of the alternator. It could safely go as high as around 17 volts. The PCM module does monitor low and high alternator output voltage.

Not sure how high the voltage is. No battery light.