Possible reasons:
1. Problems with clutch packs
* Worn or damaged friction discs
* Burnt or dirty friction linings
*Liquid leakage from the bag
2. Problems with the torque converter
* Defective torque converter clutch lock-up
* Worn or damaged pump or turbine
* Insufficient fluid
3. Problems with shift solenoids
* Faulty or dirty solenoids
* Electrical problems with wiring or transmission control unit
4. Problems with the electronic control unit (ECU)
* Software faults
* Damage to wiring
5. Insufficient fluid level
* Leak from gearbox
*Diluted or contaminated liquid
6. Other mechanical problems
* Worn bearings
* Faulty shaft or gears
* Damaged speed sensor
Diagnostics and repair:
1. Checking the fluid level and condition: Check the fluid level in the gearbox and pay attention to its color and smell.
2. Scan Trouble Codes: Use OBD2 scanner to read transmission related trouble codes.
3. Visual Inspection: Inspect the transmission for leaks or damage.
4. Fluid Pressure Check: Use a pressure gauge to check the transmission fluid pressure.
5. Test Drive: Take a test drive to check the transmission behavior during acceleration, shifting and braking.
6. Disassembly and Inspection: If necessary, disassemble the transmission to inspect the friction discs, torque converter, solenoids and other components.
After repair:
* Replace all transmission fluid.
* Reprogram the ECU (if required).
*Take a test drive to ensure the problem is resolved.
*Service your transmission regularly by changing the fluid and filter according to the manufacturer’s recommendations.