Possible reasons for increased speed on an automatic transmission:
Mechanical problems:
* Torque converter clutch slippage
* Worn or damaged clutch discs
* Coking of solenoids or valves
* Transmission fluid leaks
Electronic problems:
* Malfunction of the throttle position sensor
* Vehicle speed sensor malfunction
* Malfunction of transmission fluid temperature sensor
* Problems with the transmission control module (TCM)
Transmission fluid problems:
*Low fluid level
* Contaminated or old fluid
* Wrong fluid type
Symptoms indicating increased speed:
*High engine speed at idle
* Slow acceleration or slipping
* Rough gear shifts
*Transmission overheating
* Strange noises or vibrations
Diagnostics and troubleshooting:
* Diagnostics with error code scanner
* Checking the level and quality of transmission fluid
* Checking sensors and solenoids
*Service or replace transmission components as needed
Warning: High RPM may indicate serious transmission problems. If you notice any of the following symptoms, have your vehicle inspected and repaired immediately by a qualified mechanic. Driving with a faulty transmission can cause further damage and costly repairs.