Yes, a car with an automatic transmission will roll back on a hill if the throttle isn't engaged to add power to counter the pull of gravity. Normally not an issue as most folks come off of the brake and add throttle quickly enough so rollback is minimal. But just a side note.
Can an automatic car roll in park?
It's perfectly normal for your automatic transmission vehicle to move an inch or two after shifting it to park, such mechanical play is common even for modern cars. But if your vehicle rolls more than a few inches in Park position, it might be a sign that your transmission is faulty.4 Oct 2019
Why do some automatics roll back?
The reason why automatic cars roll back on a hill is due to the force of gravity that is exerted on your car. So, when you release your brake on a hill, what happens is that the gravity may push your car back a bit before your vehicle gets the acceleration force it needs to go against gravity.
Why would a car roll while in park?
Due to the mechanic set up of your transmission system, it's normal for your vehicle to move a few inches since the parking pawl in your transmission system is engaging your output shaft. Therefore, when your vehicle is in the park, the parking pawl will wing towards the output shaft, triggering the roll.7 Jan 2020
Does transmission spin when in park?
Yes they are. These helically cut gears are in continuous mesh with the drive line coming from the motor. With the stick unengaged and the clutch clamping down, the whole transmission spins with idle save for the output shaft itself.
Does putting a car in Park stop it rolling?
There are certain parts of your transmission system that are responsible for this action, especially if you are packed on a hill. Your automatic transmission has a device known as a parking pawl. This device locks the transmissions output shaft, preventing it from moving when your shifter is in Park.4 Oct 2019