Checking in a static position
* Move the selector lever to Park (P) position.
* Start the engine.
* Press the brake pedal and alternately switch the selector lever to each position (P, R, N, D and back). You should feel a characteristic click when switching.
Check in motion
* Accelerate to a moderate speed (about 40 km/h).
* Release the gas pedal and check for smooth gear shifting. Gears should shift smoothly and without slipping.
*Press the gas pedal to accelerate and check that the gears downshift smoothly and at the correct points.
* Reduce the speed to idle and check if the torque converter locks up (if desired). When the torque converter is locked, the engine speed should remain constant while driving at a constant speed.
* Stop the car and use the gas pedal to keep the engine speed high. Check if the transmission downshifts when you press the brake pedal.
* If necessary, check the operation of the kickdown mode by sharply pressing the gas pedal. The transmission should immediately downshift for maximum acceleration.
Additionally
* Check the level and condition of the transmission fluid. It should be at the appropriate level and a clear red or reddish brown color.
* Listen for any unusual noises or vibrations while driving.
* If the transmission is not operating properly, the transmission malfunction indicator may light up on the instrument panel.
*If you have any doubts or problems, contact a qualified mechanic for further diagnosis and repair.