When switching on the transmission:
*Low transmission fluid (ATF) level
* Worn or dirty solenoids
* Clogged ATF filter
When changing gears:
* Worn or loose clutches
* Faulty speed sensors
* Problems with the hydraulic control unit (TCU)
When the car is moving:
* Faulty torque converter
* Worn bearings or gears
*Differential problems
Other reasons:
* Wear of the ECU (engine control module)
*Wiring fault
* Problems with the engine or transmission pendulum mount
*Low ATF pressure due to faulty oil pump or pressure valve