At higher mileages, (125,000-150,000) the automatic transmission may not shift correctly. This can be caused by the throttle position sensor being out of adjustment or a shift solenoid needing to be replaced. Typically the transmission does not need to be completely overhauled.Google+
Car Problem Reports
Geo Prizm Automatic Transmission May Not Shift Correctly at High Mileages
Geo Prizm Problem
Average Mileage: 156,131 mi (130,000 mi - 197,000 mi)
Visitor, 1994 Geo Prizm, 132,787 mi
On a cold start, the car won't shift into high gears until it has warmed up. My driving is all highway and I'll be cruising at 65 mph in 3rd gear. I can barely hear myself think until it suddenly decides that it should sift.
I haven't had it fixed as I've already ordered a new car and don't want to be putting money into this.
Visitor, 1991 Geo Prizm, 160,000 mi
same problem, will not shift until it warms up to operating temperature
Visitor, 1997 Geo Prizm, 153,000 mi
shifted like a stick shift from 1st to 2nd.
My car can't even pick up the second shift!:-/
Visitor, 1996 Geo Prizm, 130,000 mi
Major forward gears slipping. Reverse ok.
Visitor, 1997 Geo Prizm, 197,000 mi
When cold and sometimes not the car will not sift correctly.
Visitor, 1996 Geo Prizm, 173,266 mi
unless at operating temp the trans does not shift into overdrive, throwing dtc, shift solenoid E