Anonymous
Anonymous asked in Cars & TransportationMaintenance & Repairs · 2 months ago

why is it normal for a vehicle to roll a few inches after parking in gear on a hill?

how depends if a manual shift or automatic?  what is happening? and does it do any damage for that to happen? why, how depends?

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  • 2 months ago
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    When you stop a car with an automatic transmission with the brakes, and put it into 'park' it engages a 'parking pawl' that locks into one of the notches of the metal ring attached to the output shaft of the engine, but it doesn't fully engage until you let off the brake and let the car roll forward, taking all of the slack out of all drivetrain components - at which point you can engage the parking brake.

    When you stop a car with a manual transmission with the brakes, turn it off, and leave it in 1st gear, the non-running engine itself acts as resistance to stop the car from rolling, but again, until you let off the brake, the drivetrain still has slack.  Depending on the engine, and the incline the vehicle is parked on, the engine may or may not be capable of fully holding the drivetrain back, so the parking brake must be engaged (and the transmission left in 1st).

    In both cases, just slowly let off the brake, and let it roll forward (or back) until it stops, then engage the parking brake, and you won't do any damage.  I've seen people put automatic vehicles into park while the car is still moving forward and you will hear the parking pawl click a few times (that's not good).

    I occasionally turn the engine off in my manual transmission vehicle as I am coming to a stop and let the engine slow it down (probably not suggestable) or even just leave it in gear while running and let it stall (mostly for my own amusement, and again - probably not suggestable).

    Cars can take quite a bit of abuse, but if you have a car that you want to last a while, it's a good idea to minimize unnecessary wear and tear.

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