Possible causes of automatic transmission knocking when engaging reverse gear:
* Damaged torque converter: This device transfers power from the engine to the transmission. A knocking noise can occur when the torque converter blades are worn or damaged.
* Faulty reverse pump: This pump creates pressure to engage reverse gear. The knocking noise may be caused by a malfunction of the pump or its valves.
* Worn reverse clutches: Clutches engage reverse gear. A knocking noise can occur when these clutches are worn or damaged.
*Low transmission fluid level: Insufficient fluid level in the automatic transmission can lead to inadequate lubrication and knocking noises when engaging reverse gear.
* Electronics problems: Some automatic transmissions are controlled by an electronic control unit (ECU), which can malfunction, causing knocking noises when shifting gears.
* Faulty gear selector: The gear selector tells the transmission which gear to engage. A faulty selector may give incorrect commands, causing knocking noises when engaging reverse gear.
* Damaged driveshaft: The driveshaft transfers power from the transmission to the rear wheels. A knocking noise can occur when the driveshaft or its connections are worn or damaged.
*Worn Engine or Transmission Mounts: Loose or worn mounts can allow the engine or transmission to move, resulting in a knocking noise when shifting into reverse.
Diagnosis of the problem:
To diagnose the cause of the knocking noise, you may need the following:
*Checking the transmission fluid level
* Scan the ECU for fault codes
* Inspection of torque converter, reverse pump and clutches
* Checking the driveshaft and supports
* Monitoring the transmission while engaging reverse gear
Repair:
Depending on the reason for the repair, the following actions may be required:
* Replacing the torque converter
*Reverse pump repair
* Replacing reverse clutches
* Topping up transmission fluid
* ECU repair or replacement
* Gear selector replacement
* Repair of cardan shaft
* Replacement of engine or transmission mounts