How does a parking pawl work?
The parking pawl works by engaging a metal pin "pawl" into one of the notches of a metal ring that is attached to the transmission's output shaft when the shifter level is placed in the Park position. When the pin is in this position, the output shaft is prohibited from turning, which in turn prohibits the drive wheels from turning. Moving the shifter out of Park disengages the pin, which frees the output shaft and drive wheels to turn freely.
NOTE: Relying solely on the transmission's "Park" position and the parking pawl to keep the vehicle from rolling when parked places undue stress on the pawl and other driveline components, which can cause excessive wearing of the pawl and lead to premature failure. See Important Tip below.
Symptoms of a worn or broken parking pawl
If your vehicle rolls forward or backward more than an inch or so after placing the shifter into the Park position, the parking pawl may be badly worn. If your vehicle rolls more than a couple of inches, or rolls freely, after placing the shifter into Park, the parking pawl may be broken.
In a rear wheel drive vehicle, a worn out universal joint (or U-Joint) can also cause excessive vehicle roll after the shifter lever is placed into Park. In fact, a worn out U-joint is much more common than a worn or broken parking pawl. Therefore, you must rule out the universal joint as the cause of excessive roll. The cost to replace a U-joint is less than $40. The cost to replace a parking pawl is at least $500, unless you do-it-yourself.
