Parking pawl
Encyclopedia
A parking pawl is a device fitted to a motor vehicle
Motor vehicle
A motor vehicle or road vehicle is a self-propelled wheeled vehicle that does not operate on rails, such as trains or trolleys. The vehicle propulsion is provided by an engine or motor, usually by an internal combustion engine, or an electric motor, or some combination of the two, such as hybrid...

's automatic transmission
Automatic transmission
An automatic transmission is one type of motor vehicle transmission that can automatically change gear ratios as the vehicle moves, freeing the driver from having to shift gears manually...

 in order for it to lock up the transmission. It is engaged when the transmission shift lever
Gear stick
A gear stick is the lever used to change gear in a vehicle, such as an automobile, with manual transmission or several common forms of automatic transmission.The device is used to change gear; in a manual transmission vehicle this will normally be done whilst depressing...

 selector is placed in the Park position, which is always the first position (topmost on a column shift, frontmost on a floor shift) in all cars sold in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 since 1965 (when the order was standardised by the Society of Automotive Engineers (SAE)), and in most other vehicles worldwide.

The parking pawl locks the transmission's output shaft to the transmission casing by engaging a pawl (a pin) that engages in a notched wheel on the shaft, stopping it (and thus the driven wheels) from rotating.

Most vehicle manufacturers
Automotive industry
The automotive industry designs, develops, manufactures, markets, and sells motor vehicles, and is one of the world's most important economic sectors by revenue....

 and auto mechanics do not recommend using the transmission's parking pawl as the sole means of securing a parked vehicle, instead recommending it should only be engaged after first applying the vehicle's parking brake. Constant use of only the parking pawl, especially when parking on a steep incline, means that driveline components, and transmission internals, are kept constantly under stress, and can cause wear and eventual failure of the parking pawl or transmission linkage. The pawl might also fail or break if the vehicle is pushed with sufficient force, if the parking brake is not firmly engaged. Replacement can be an expensive operation since it generally requires removing the transmission from the car.

It is highly inadvisable to use the parking pawl to stop a vehicle in motion. Modern parking pawls are connected to a safety mechanism that prevents the pawl from engaging unless the vehicle is stopped first. The pawl mechanism is generally not strong enough to stop a vehicle in motion, if it engages at all. Under that much stress, the pawl may simply break off in the transmission, leading to costly repairs.

External Links

  • http://ken-gilbert.com/wrx/STi_Manual/04.%20TRANSMISSION/02.%20AUTOMATIC%20TRANSMISSION/33.%20Parking%20Pawl.pdf
  • http://www.driversedguru.com/driving-articles/car-auto-maintenance/always-set-the-parking-brake/
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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