Possible causes of knocking noise when engaging reverse gear:
Transmission problems:
* Worn synchronizers
* Faulty clutches
* Damaged planetary gear
*Low transmission fluid level
* Contaminated transmission fluid
Problems with the driveshaft:
* Unbalanced driveshaft
* Worn spline joints
* Damaged crosspieces
Differential problems:
* Worn differential bearings
*Bent differential axle
*Low transmission fluid level in differential
Other possible problems:
* Faulty reverse position sensors
* Damaged electrical connectors
* Worn motor mounts
* Incorrect shift cable adjustment
* Insufficient oil supply to reverse gear
Diagnostics:
To diagnose the problem and determine the exact cause of the knocking, you must perform the following steps:
* Check the level and condition of the transmission fluid.
* Start the engine and engage reverse gear.
* Listen to the nature of the knock and its location.
* Use a scanner to read fault codes.
* Visually inspect the transmission, driveshaft and differential for leaks, damage or signs of wear.
Troubleshooting:
Once the cause of the knocking noise has been determined, appropriate troubleshooting must be carried out, which may include the following:
* Replacement of synchronizers or clutches
* Repair or replacement of planetary mechanism
* Adding or replacing transmission fluid
* Balancing the driveshaft
* Replacement of worn or damaged parts
*Adjusting the gear shift cable
* Installation of new motor mounts
* Replacement of reverse position sensors
* Solving problems with electrical connectors
* Ensure proper lubrication of reverse gear