Possible reasons:
*Low transmission fluid level: Check fluid level and add if necessary.
* Contaminated transmission fluid: Replace fluid and filter according to manufacturer’s recommendations.
* Worn gaskets or seals: Replace faulty gaskets or seals that may be causing fluid leaks.
* Faulty Shift Solenoid: The solenoids control the gear shift. Replace faulty solenoids.
* Worn or damaged torque converter: The torque converter transfers power between the engine and transmission. Replace the faulty torque converter.
* Transmission Control Module (TCM) software problems: Update or reprogram the TCM.
*Transmission Mechanical Problem: This is a more serious problem that may require the transmission to be removed and rebuilt.
Diagnostics and repair:
* Check the level and condition of the transmission fluid.
* Scan the system for trouble codes.
* Perform a visual inspection of the transmission and surrounding components for leaks or damage.
* Check the operation of the solenoids and torque converter using specialized equipment.
Depending on the diagnosed causes, repairs may include replacing the fluid and filter, replacing faulty components, or rebuilding the transmission. It is recommended to contact a car repair shop for professional diagnostics and repairs.