What are the effects of shifting to P gear before the automatic transmission car comes to a complete stop?

[DelLeonardo]

When an automatic transmission car hasn't come to a complete stop, the output shaft of the transmission is still rotating. Directly shifting into P gear engages the parking pawl with the parking gear, forcibly locking the still-rotating output shaft, which can cause damage to the vehicle. Here's an introduction to automatic transmission gears: 1. P gear: The P gear is used when parking by moving the gear selector to the P position, which locks the transmission's parking mechanism to secure the output shaft. Combined with the handbrake, this prevents the car from moving. 2. R gear: The R gear is the reverse gear, used when backing up. Never shift into reverse before the car has completely stopped, as this will cause rapid wear to the transmission. 3. D (drive) gear: The D gear represents the drive gear for normal forward driving. With the gear selector in D position, the car automatically shifts gears while driving. During long descents, since D gear doesn't provide engine braking, you shouldn't keep it in D gear continuously, otherwise the speed will keep increasing, raising safety risks. 4. L gear: The L gear is the low gear, equivalent to 2nd gear, often used when going up or down hills. 5. S gear: The S gear stands for sport mode, available in some models. In S gear, the car can shift freely but with some delay, keeping the engine at higher RPMs longer, which increases fuel consumption but provides greater torque output, typically used for overtaking. 6. N gear: N represents neutral, used when starting the car or towing. If waiting at traffic lights for extended periods, it's best to shift to N gear and apply the handbrake. However, coasting in neutral (N gear) downhill is prohibited as it not only doesn't save fuel but can damage the transmission. 7. M gear in manual-automatic models: M stands for manual mode. When switched to M gear, you can shift gears manually as needed by pushing "+" or "-" or using paddle shifters.

[VanCooper]

That day I was in a hurry and shifted into P before the car came to a complete stop. The transmission made a loud BANG sound that scared me to death! Later, the mechanic told me that automatic transmissions have a small parking pawl inside - forcing P while moving is like trying to hook a spinning gear with an iron claw, which really damages the transmission. At best, it deforms the pawl and requires a small part replacement; at worst, it can crack the entire transmission case with repair costs over 10,000 yuan. I was lucky that time - only needed to replace the parking pawl, but it still cost me over 1,000 yuan. Now I always firmly press the brake and wait until the car is completely stationary before shifting to P. Seriously, don't risk major expenses just to save those two seconds.

[DelGemma]

Let me tell you, this operation really hurts the car. The P gear's locking mechanism is just a small pawl with a hook. It can only securely engage with the transmission gear slot when the car is completely stationary. If the wheels still have momentum and you forcefully shift into P gear, the hard impact is entirely absorbed by the transmission, which can bend the pawl or even break the gear teeth. Especially when parking on a slope, you need to be extra careful. If the car rolls slightly and you shift into P gear, the impact is even greater. I've seen cases where the transmission casing was cracked and leaked oil due to this. Nowadays, cars have protection mechanisms, and some newer models won't allow shifting into P gear under such conditions, but for older cars, it's better to be cautious. Hold the brake, wait for the car to stabilize, and then move the gear lever—that's the safest way.

[Bill]

Never do this! Shifting into Park (P) while the car is moving forces the transmission to lock. The wheels are still turning, and that tiny parking pawl has to withstand enormous kinetic energy—it can break or deform in just one attempt. I've handled many such repairs, with transmission valve body damage being the most common, and in severe cases, the entire transmission is scrapped. That 'click' sound you hear? It'll cost you at least a few thousand bucks to fix. Remember the mantra: Come to a complete stop → press the brake pedal firmly → shift to Neutral (N) and engage the parking brake → release the foot brake to confirm the car doesn't move → finally shift to Park (P). Developing this habit can save you a lot of money.