What causes a sudden thud sound when shifting gears in a car?

[MacJulia]

When shifting gears in a car, a sudden thud sound may be caused by loose friction plates on the steel plate or impact noise between the release lever and the window hole. Below is an introduction to car gear shifting: 1. Introduction: It should be referred to as "gear shifting". Gear shifting refers to the transmission, which is used to change the torque and speed of the engine crankshaft. 2. Function: To meet the different requirements of driving wheel traction and speed under various driving conditions such as starting, accelerating, driving, and overcoming road obstacles. 3. Techniques: First, remember the principle of "accelerate before upshifting, decelerate before downshifting" when shifting gears. Before upshifting, "rev" the throttle to increase the speed first, and before downshifting, "release" the throttle to reduce the speed first.

[VanLucy]

I also encountered a similar situation before. A friend at the repair shop mentioned several common causes: loose transmission mounts can cause metal parts to collide and produce noise; excessive wear in the driveshaft leading to increased gaps can result in metal clunking sounds when shifting gears; severe wear in the CV joint can also cause abnormal noises when the load changes. I remember that time we also found that the engine mount rubber had aged, causing the engine to shift, making the entire powertrain shake every time I shifted gears. The worst was the internal gear teeth grinding in the transmission—the sound was as loud as banging on a metal bucket. This issue shouldn’t be delayed. Last time I procrastinated, the repair cost doubled. It’s best to check the chassis and suspension system immediately, especially for automatic transmission cars—if this sound occurs frequently, it’s likely a transmission problem.

[LaAmelia]

Having driven manual transmissions for over a decade, I'm all too familiar with gearshift noises. When the clutch doesn't fully disengage, you get that clunking sound during gear changes - exactly like the 'dong' you described. Cars with worn synchronizers also make this noise, especially noticeable in older vehicles where gears can't mesh smoothly and end up grinding. Always check if your transmission fluid has deteriorated - low fluid levels or poor-quality oil will cause dry friction in the shift mechanism. Last time I helped a friend troubleshoot, we found stiff shift cables causing excessive impact during engagement. These sounds often come with noticeable body vibrations too. Remember to avoid forced gear engagement - if the noise persists after warming up, it's time for a transmission teardown inspection.

[RebeccaAnn]

Last time during car repair, the technician analyzed that gear shifting noise is mainly caused by mechanical impact. For automatic transmissions, it could be due to power connection impact caused by torque converter failure; for manual transmissions, it's likely due to clutch pressure plate deformation or flywheel unevenness. For older cars, it's also necessary to check if the shift mechanism bushings are worn out—excessive clearance will cause impact. Modified cars need extra attention to incorrect driveshaft angles, as universal joints may collide during gear shifting. When this thud sound occurs, pay attention to its frequency—occasional noise when the engine is cold is not a big issue, but if every gear shift is accompanied by vibration, it's dangerous.