With my 95 Saturn SL2 (about 150,000 miles), I am finding that after the car has warmed up, it sometimes/regularly slips or won't upshift to one or more higher gears. If I stop, turn the car off even for a moment and restart, it is immediately fine again, at least temporarily. From this I am guessing that I am dealing with something other than a mechanical problem, perhaps a sensor or connection or computer control. Since the 95 is pre-OBDII, I was able to check the Diagnostic Trouble Codes manually. I show only these codes (transaxle, not engine):
22 (no 2nd gear)
23 (no 3rd gear)
24 (no 4th gear)
Anyone recognize this set of symptoms?