Why does your car jerk when you let off gas after shifting?

When shifting, the transmission helps connect or remove torque from the driveshaft to increase or reduce the vehicle speed. As the torque is added or reduced, the car experiences a subtle jolt of acceleration or deceleration. These jolts are more noticeable when the gearshift is done abruptly, the revs aren't equal during up or downshifts, or when the clutch is released too quickly (in a manual).

In an automatic transmission, gearshifts can result in a slight jerk because of the gear change and a slight surge in engine speed. In such cases, it is usually more noticeable when the vehicle is accelerating hard or shifting gears at lower speeds, such as when coming to a stop. Worn or damaged transmission components, such as worn clutch plates, low transmission fluid, or issues with the shift solenoids, can contribute to more pronounced jerking.

In manual transmission vehicles, sudden release of the clutch pedal after changing gear can cause the engine speed to drop, resulting in a jerk as the torque suddenly engages. A rough or incomplete downshift can also lead to a jerk. Smooth shifting involves matching engine RPMs to the chosen gear, which minimizes these jolts.

It is important to note that a slight jerking sensation during shifting is normal, especially in older or less refined drivetrains. However, if the jerking is excessive or the vehicle's shifts feel unpredictable or jerky at unusual times, it is advisable to have the vehicle inspected by a professional mechanic to diagnose and address any potential problems with the transmission or other drivetrain components.