Causes of knocking noise when shifting gears on an automatic transmission:
1. Low transmission fluid (ATF):
* Insufficient fluid can result in insufficient lubrication of the internal components of the transmission, causing friction and knocking.
2. Dirty or degraded ATF:
* Over time, ATF can become contaminated and lose its lubricating properties. This can lead to increased wear and noise.
3. Worn or damaged gears:
* Gear teeth can wear over time, resulting in slippage and noise when shifting gears.
4. Faulty torque converter:
* The torque converter helps transfer torque from the engine to the transmission. Air pockets, clogs, or mechanical problems can cause the knocking noise.
5. Worn friction bands or discs:
* These components help engage or release the gears. Their wear can lead to slippage, vibration and noise.
6. Faulty solenoid:
* Solenoids control the flow of ATF in the transmission. Faulty solenoids can cause rough shifting or knocking noises.
7. Worn shaft bearings:
* Bearings support rotating shafts in the gearbox. Their wear can lead to noise and vibration.
How to eliminate knocking:
* Check ATF level: Make sure the fluid level is between the “hot” and “cold” marks on the dipstick. If necessary, add ATF.
* Replace ATF and filter: Periodically replacing the ATF and filter helps maintain the cleanliness and lubricating properties of the fluid.
* Run a transmission diagnostic: A mechanic can use a scan tool to check fault codes and identify faulty components.
*Transmission Repair or Replacement: In cases of serious problems, the entire transmission may need to be repaired or replaced.