Possible reasons:
1. Worn or damaged torque converter:
* Knock when shifting gears or engaging reverse.
* May increase with increasing engine speed.
2. Oil pump problems:
* Noise and vibration when changing gears.
* May be accompanied by oil leakage from the automatic transmission.
3. Worn or damaged planetary gear:
* Knocking or grinding noise when shifting gears.
* May be especially noticeable when shifting from first to second gear.
4. Problems with solenoids:
* Knocking or clicking noise when shifting gears.
* May be accompanied by problems with gear shifting.
5. Worn or damaged clutch:
* Slippage or delay when shifting gears.
* May be accompanied by knocking or noise.
6. Low level or contamination of transmission fluid:
* Knock or vibration when shifting gears.
* May cause overheating and further damage to the automatic transmission.
7. Wear or damage to friction discs:
* Knock or noise when shifting into gear.
* May be accompanied by slippage or vibration.
8. Malfunction of sensors and electronic components:
* Knocking or grinding noise when shifting gears.
*Can be caused by faulty speed, position sensors or solenoids.
Recommendations:
*Consult a qualified mechanic who specializes in automatic transmission repair to diagnose and repair the problem.
* Maintain the automatic transmission regularly, following the manufacturer’s recommendations.
* Use the correct type of transmission fluid for your vehicle.
* Avoid sudden acceleration and braking, which can damage the automatic transmission.