You Accidentally Shifted Into Park While Driving. Did You Just Damage Your Transmission?

Sometimes, we all do dumb things. Well, this time you’ve really done it — you shifted the car into park when it was on the move. More likely than not, you then immediately heard the car make a terrible scraping noise. What just happened? Did you just damage your transmission? Do you have an expensive repair in your immediate future?

Unfortunately for you, the news isn’t good. That scraping noise was indeed your transmission, which is sadly one of the more expensive parts of your already expensive car. If it was only for a second or two, odds are you’ll probably skate through alright, but even then, probably best to swing by your mechanic of choice and get it looked at. If there really is an issue now, you’ll want to get that fixed as soon as possible. In an extreme case, your parking gear might not work at all now, in which case you’ll have to rely on the handbrake or emergency brake until you get it repaired.

That P on your shifter isn’t a gear in the strictest sense. Instead, shifting to park engages a little device called a parking pawl, which is really just a simple metal hook on a spring. 

When in park, that spring shoves the hook down, which will then latch into the teeth on the output shaft of the transmission. Once hooked in, the shaft stops spinning. Since the transmission, well, transmits its spin eventually down to the wheels, which is what moves your car, stopping the transmission stops your car. Now you’re parked. If the pawl happens to come down outside of the tooth, your car will have to roll for just a moment until a tooth moves into place. This is why your car has that split-second roll once you take your foot off the brake.

This is all fine and good when the car is stopped. If you’re on the move, however, the output shaft is spinning quickly — too quickly for the pawl to latch into the teeth, so the pawl will be scraping and skipping along them instead. That can potentially damage either the teeth or the pawl itself, effectively breaking your parking gear. Worse, there’s even a chance that shredded metal will get into your transmission, which can cause all sorts of damage.

Modern cars are pretty smart, and their computers probably won’t let you make this mistake in the first place. Even so, best to be careful.