Why does the car make a thud sound when the transmission overheats?
3 Answers
It could be due to wear and tear of transmission bearings or gears, or bearing spots. When accelerating and shifting gears, abnormal noises from the transmission may indicate the presence of metal powder in the transmission oil, suggesting excessive wear of components such as brake bands and clutches inside the transmission. Solutions: The transmission consists of numerous parts, and the causes of noise are relatively complex. When analyzing and diagnosing, pay attention to the following: whether the noise is related to specific speeds, as some planetary gears may produce noticeable noises around 50Km/h. Whether the noise is related to certain gears, which is crucial for diagnosing transmission issues. If noise occurs in a specific gear, it is certainly related to the components affecting that gear's transmission; if noise occurs in all gears, it is often due to faults in the constant-mesh gear shaft or insufficient transmission oil. Whether the noise is related to specific actions, such as shifting gears, starting, rapid acceleration, rapid deceleration, or turning, all of which are effective means for diagnosing abnormal noises. Among these, changing speed and direction are particularly important for determining rear axle faults.
The transmission overheated and made a 'thud' sound. I remember encountering a similar situation when driving uphill before. That kind of sound is usually caused by metal components expanding due to heat and then colliding. When the oil temperature is too high, the internal gears and other components of the transmission expand and contract with heat. If a part is deformed or worn, it may produce a 'thud' impact sound. It could also be the automatic transmission's torque converter malfunctioning under high temperatures, causing shocks during locking or unlocking. Other causes include degraded or contaminated fluid, a blocked cooling system leading to poor heat dissipation, or prolonged towing without downshifting. I suggest pulling over immediately to let the vehicle cool down if you hear this sound—never continue driving, as it could cause more severe damage, such as burning out the entire transmission. Regularly check the transmission fluid level and quality, replace the filter on time, and avoid continuous high-speed driving in hot weather to prevent overheating.
I heard a thud from the transmission while driving, most likely caused by overheating. The sound resembled something hitting the casing, possibly due to internal pressure changes from rising oil temperature, gear deformation, or fluid boiling. Overheating often stems from poor driving habits, such as prolonged high RPM in low gear on steep slopes, running the AC at full blast increasing load, or insufficient transmission fluid and cooling fan failure preventing effective heat dissipation. I remember being terrified the first time it happened, but understanding the cause actually eased my fear: such abnormal noises are warning signals indicating the transmission is operating under excessive load. To avoid more severe issues like component failure or uncontrolled oil temperature, I must immediately pull over, turn off the engine, and let the car cool for half an hour before inspection. Routine maintenance is recommended to ensure the transmission system remains in good condition.
