What is the reason for jerking when the clutch is released quickly during gear shifting?

[VanStephen]

The reason for jerking when the clutch is released quickly during gear shifting is the difference in rotational speed between the engine and the clutch disc. Detailed explanation: When there is a rotational speed difference between the engine and the clutch, the engagement between the clutch and the engine is imperfect. The interaction of forces between the clutch and the engine causes gear shifting jerks. Gear shifting timing: Gear shifting timing is primarily based on vehicle speed. Within the same gear, once the vehicle reaches the appropriate speed for shifting, the engine speed will not fall below the required level. However, the reverse is not necessarily true—the engine speed may reach the required level while the vehicle speed may not meet the shifting conditions (possibly due to clutch slippage or the clutch pedal not being fully released). For manual transmission compact cars, when shifting from 2nd to 3rd gear, the vehicle speed should be above 35 km/h to reach the appropriate shifting speed. (Unless driving uphill, where the shifting speed may be slightly increased.)