Reasons for slipping in the reverse gear of an automatic transmission:
Mechanical problems:
* Worn or broken torque converter
* Wear of friction discs or steel plates
*Damage to sun gear, planetary gear or output shaft
* Malfunction of oil pump or lines
*Low or dirty transmission fluid
* Clogged hydraulic channels
Problems with the electronic part:
*Transmission control module (TCM) malfunction
*Damage to input and output shaft speed sensors
* Malfunction of pressure control solenoids
Other possible reasons:
* Faulty gear selector
* Mechanical damage to the gearbox due to impact or accident
* Unstable power supply or grounding
*Using incorrect or inappropriate transmission fluid levels
Additional factors that can aggravate slippage:
*Cold weather and thick transmission fluid
* Excessive load on the vehicle (for example, towing)
* Aggressive driving style