I drive a '99 toyota corolla with automatic transmission. I have noticed that the car becomes jerky during gear changes as the car picks up speed.

Some possible causes could be a worn valve body, contaminated gearbox oil, faulty transmission control unit, worn gear cogs, or even the selector switch not being in sync.

Your throttle position sensor may be in need of calibration as well. Change the gearbox oil first and monitor the situation. If the problem persists, your gearbox unit might need an overhaul -  torque converter included.

If your workshop has an On Board Diagnosis (OBD) tester, request for your mechanics to conduct a check to first identify the possible faults.

Karen Choo
Corporate Communications
Automobile Association of Singapore