If you've ever seen a car that rolls or inches ever so slowly downhill while in park, you've seen a car with a transmission pawl problem. Many people don't give any thought to leaving their car parked on a hill without engaging the parking brake, until they get a bill for expensive repairs. Or worse, their car rolls downhill and damages someone's property.
The transmission pawl in an automatic transmission is a pin or lever attached to a spring that engages when the car's gear shift is in the "Park" position. For this reason, it's also referred to as the parking pawl. It stops the gears in the transmission from rotating, keeping the car stationary while in park. Manual transmissions do not have a parking pawl. In a manual transmission, the clutch disengages the gears, but the output shaft still rotates.
If the car is parked on steep hills with only the parking pawl engaged, it can cause wear on the pawl. This can result in the car creeping downhill as the pawl slips out of the notch. If you hear grinding from the transmission when the car is parked on an incline or it starts to slowly roll, you have a parking pawl problem.
Fixing the parking pawl on an automatic transmission requires opening the transmission case. Depending on the car, it may require pulling the transmission out entirely. It's one of those jobs that isn't difficult to do once you have access to the part, but getting access to the part may require specialized tools. If you are experienced with working on automatic transmissions, you can fix the problem yourself. If you're not comfortable working on cars, talk to the local car dealer or mechanic about the cost of fixing the problem.
Car manufacturers recommend that the driver always use the parking brake when parking on an incline. Engage the parking brake before putting the car in park. This will keep the pawl from becoming worn. It also provides additional security, should your car be hit by another car while in park. If the parking pawl has given out, you can still drive the car normally. You will need to put chocks under the wheels when parking on a hill.
