Why does my engine slip when the car gets hot and why does the speedometer and the RPM needle go hay wire when the car gets hot?
Why does my transmission slip when the car gets hot? on 1999 Toyota Camry
Has the yellow "Check Engine Light" come on? If so a scan tool will be needed to retrieve codes stored in the computer of your car. Speedometer and RPM needle could be sign the problem is electrical (external from the transmission which would be good news). Servicing the transmission may be the first and cheapest place to start. In servicing the transmission the condition of the oil will be checked, the oil can be checked for debris, the filter and magnets at the bottom of the oil pan can be inspected, and on a test drive afterward the shifting of the transmission can be checked to see if the transmission may have further mechanical or electrical problems.