Possible causes of a metallic knock when shifting an automatic transmission:
1. Low transmission fluid level:
* When the fluid level is too low, there is not enough lubrication in the gearbox. This may cause friction between metal parts and cause knocking noise.
2. Worn friction discs:
* Friction discs help transfer power between shafts in the transmission. Their wear can cause slippage and vibration, which can cause knocking noises when shifting gears.
3. Faulty transmission solenoids:
* Solenoids control the flow of fluid in the transmission. Faulty solenoids can cause gears to shift incorrectly, which can cause a knocking noise.
4. Damaged torque converter:
* The torque converter transfers power from the engine to the gearbox. Damage to the torque converter, for example due to worn bushings, can cause a knocking noise.
5. Worn drive shafts:
* Drive shafts connect the gearbox to the wheels. Worn drive shafts can cause vibration, which can cause knocking noise.
6. Wear of gearbox bearings:
* Bearings reduce friction between rotating parts of the gearbox. Worn bearings can cause a knocking or grinding noise when shifting gears.
7. Worn gearbox gears:
*Gears in a gearbox are used to transmit power. Worn gears can cause knocking or noise when shifting gears.
8. Incorrectly configured gearbox:
*If the transmission is not set up correctly, it may not shift properly, which may cause knocking noise.
Important Steps:
* Contact a mechanic immediately to identify and repair the cause.
* Check the transmission fluid level.
* Listen to the sounds when shifting gears to determine the exact location of the knock.
*Do not ignore knocking noises as this may cause more serious damage.