My 95 Lumina with 199,000 miles on it will not always shift into overdrive. It seems to do it more when its first started for the day. I have changed trans fluid and filter regularly so I don't think its that. If is not shifting into overdrive, I have to stop the car , shut it off, then restart and it will then shift. Anyone else have this problem.

This can be a shift solenoid issue or an internal problem, get is scanned by a trans shop for a proper diagnosis.

Which trans. does it have in it?

Should be a 4t60e.

yes it is a 4t60e. Shifts into OD 95 percent of the time. If you run it around alittle before going on the road it seems fine. Its when you hit the road immediately.

Until the temps reach a preset limit it will not see o/d, pcm programming.

If it doesn't shift into OD, it never will. The only way to make it shift is to stop, shut it off, restart, then it will be fine. Crazy I know.

A trans function scanner in the hands of a trans tech can look at internal solenoid operation and pcm commands to see what the issue may be.