What Causes Transmission Noise at Idle?
2 Answers
The causes of transmission noise at idle include bearing wear, prolonged lack of transmission fluid replacement, and poor heat resistance of transmission fluid. Bearing Wear and Damage: When bearings wear out, their clearance increases and their fitting precision decreases. When bearings are damaged, abnormal noises occur as they cannot operate normally, potentially leading to damage of transmission components and further exacerbating the issue. Prolonged Lack of Transmission Fluid Replacement: If automatic transmission fluid is not replaced for a long time, it becomes thicker and loses its fluidity, resulting in insufficient lubrication between components. This leads to direct friction, accelerating mechanical wear and causing abnormal noises. Poor Heat Resistance of Transmission Fluid: Using low-quality automatic transmission fluid, which has poor heat resistance, can lead to oxidation, sludge, and residue formation. These can clog the filter screen and oil passages, increasing friction among internal transmission components and causing abnormal noises in the vehicle.
When there is abnormal noise from the transmission during vehicle idling, I have experienced it several times, with the most common issue being torque converter problems, especially in automatic transmission models. Wear of internal components or failure of the locking mechanism in the torque converter can cause friction sounds, such as rustling or rattling noises. This is often due to prolonged use or inferior fluid accelerating component aging. Loose transmission bearings or excessive gear clearance can also produce abnormal noises, which are more common in manual transmission vehicles. I recommend first checking the transmission fluid level; if the dipstick shows a low level or the fluid is black, promptly topping up or replacing the fluid can reduce the noise. Additionally, unstable idling or significant engine vibration can exacerbate the noise, so it's advisable to check whether the idle speed is normal. Don’t delay repairs, as minor issues can escalate into complete transmission failure, doubling the cost. Regular maintenance, such as changing the fluid every 40,000 kilometers, can prevent such troubles with simple steps.
