Why does the car shake when shifting into P gear?

[MacJune]

When the vehicle is parked on a slope and shifted into P gear, it may shake back and forth slightly. This actually does not cause any damage to the transmission. The reason for this is that there is a gap between the parking pawl and the parking gear. Due to the imprecise mechanical mechanism of the parking pawl, the vehicle may shake slightly after shifting into P gear and releasing the foot brake. Once the parking pawl engages firmly, the vehicle will no longer move. Many car owners mistakenly believe that this shaking is harmful to the car, but in reality, it is not a problem at all, and there is no need to worry unnecessarily. Below are some parking precautions: 1. Turning the steering wheel to the limit: The greater the steering angle, the higher the hydraulic pressure in the power steering system. When the steering wheel is turned to the limit, the power steering pump operates under high pressure. Under the same usage conditions, the failure rate increases significantly with high-intensity use. It is best to slightly release the steering wheel after turning it to the limit. 2. Shifting into reverse gear before the car comes to a complete stop: The reverse gear may produce abnormal noises due to hard impacts, leading to wear and damage to the gear teeth. Over time, this can make the gears more prone to grinding and slipping out of gear.

[OAubrey]

The body shaking when shifting to P gear is actually quite common. I was startled too when I first started driving. Essentially, it's the action of the small hook in the transmission engaging with the gear. At the moment the car stops, the transmission still has some residual momentum, and the gears are still rotating. If you abruptly shift to P gear, the hook happens to catch in the gear gap, causing a 'thud' and a shake. Later, I learned to be smarter: when parking, first press the brake and shift to N gear, wait for the car to come to a complete stop, engage the handbrake, and then shift to P gear. This trick works especially well when parking on a slope—the car stays as steady as if it's nailed to the ground. If every time you shift to P gear feels like being kicked, it's time to check the transmission mount or transmission fluid immediately.

[AugustLee]

I finally understood the principle after watching a technical video last time. When an automatic transmission is parked in P (Park) mode, the parking pawl inside the transmission locks onto the gear shaft, similar to leaving a manual transmission in 1st gear to hold the car in place. The body shaking is essentially the physical collision between the gear and the pawl. This is especially noticeable when parking on a slope, as the entire weight of the car rests on that pencil-thin pawl. If you frequently hear a 'clunk' sound, it's likely due to pawl wear or aging transmission buffer bushings. Now I've developed a good habit: on flat ground, I always engage the parking brake firmly before shifting to P. By the way, during cold starts, it's best to wait an extra half-second before shifting, as insufficient oil pressure can cause jerky movements.

[DiLola]

Auto mechanic Old Zhang explained this to me. The moment an automatic transmission car is shifted into Park (P), a metal latch from the parking lock mechanism inside the transmission pops out. If the wheels still have slight rotation, the latch hits the rotating gear shaft, naturally causing the car body to shake. It's like suddenly jamming a bicycle kickstand into a spinning wheel. When parking on a slope, don't shift directly into P; instead, first press the brake, shift to Neutral (N), engage the handbrake, release the brake to let the car settle, and finally shift into P. If the shaking is severe every time, it's recommended to check the transmission mount rubber, as its shock absorption deteriorates when aged.