Is it harmful to the car if it stalls in D gear?
4 Answers
Stalling in D gear does not affect the car. Here is some relevant information about car stalling: Causes of stalling: The main reasons for car stalling include damage to electronic components in the cooling system (thermostat, cooling fan), poor radiator performance, and insufficient coolant. What to do after stalling: Pull over to the side of the road, but do not turn off the engine immediately. Since the coolant temperature is already very high and its cooling capacity has reached its limit, immediately turning off the engine would stop the circulation of the boiling coolant. Instead, let the engine idle for a while, as the continuously circulating coolant can still help mitigate the impact of high temperatures on the engine.
That time I met a car owner during a repair job. His car had severe gear shifting jerks, and upon opening the transmission, we found the clutch plates were unevenly worn. Checking the dashcam revealed he often stalled the engine in D gear, causing the locking mechanism to be pitted from impacts. The transmission fluid had excessive metal shavings, and the repair cost him over ten grand. Actually, when the engine stalls, power is still being transmitted, and a sudden power cut is like slamming the brakes on high-speed gears, potentially deforming the gear clearance. The parking pawl suffers even worse, as the twisted force angle can grind grooves into it. It's recommended to develop a three-step parking habit: firmly press the brake and shift to N, engage the handbrake and release the foot brake, and only shift to P and turn off the engine after the car is completely stationary. This way, your transmission can stay healthy even after ten years of use.
Once I forgot to shift gears after reversing and turned off the engine, causing the car to suddenly lurch forward—luckily, there was no car behind me. When I took it to the auto repair shop for inspection, the mechanic used an OBD scanner to check for trouble codes and said it was no big deal—the solenoid valve protection function had kicked in. He reminded me that it’s like suddenly squeezing the front brake on a bicycle: the chain and gears might clatter, but they won’t break after just one or two occurrences. If I was really concerned, he suggested checking the transmission fluid color—if it’s black, it indicates clutch plate wear. That time, I spent over 300 yuan on a fluid change. Since then, I’ve remembered to wait for the tachometer to drop to zero after coming to a complete stop before turning off the engine. Otherwise, the next time I start the car and turn the key to the ON position, the transmission might still be in D gear, causing a sudden jerk.
From a design principle perspective, modern transmissions feature dual protection mechanisms: the oil pump stops immediately upon engine shutdown, and the clutch automatically disengages to prevent hard friction; the ECU cuts off ignition signals upon detecting abnormalities. However, long-term engine shutdown in D gear still poses three risks: first, sudden oil pressure changes may impact the shift valve body, potentially causing jamming and resulting in gearshift jerks; second, the locking mechanism bears additional torque, affecting parking reliability; third, restarting causes current surges to the motor control system. It's recommended to develop the habit of fully depressing the brake pedal before shutting off the engine - this allows the torque converter to absorb up to 70% of the impact even when left in D gear.
