A parking pawl is a device fitted to a motor vehicle's automatic transmission that locks up the transmission when the transmission shift lever selector is placed in the Park position. "Park" is the first position of the lever (topmost on a column shift, frontmost on a floor shift) in all cars sold in the United States since 1965 (when the order was standardised by the Society of Automotive Engineers (SAE)) through SAE J915,[1] and in most other vehicles worldwide.
Interior of an automatic transmission, showing the toothed locking wheel and the pawl below it; a finger is touching the pawl
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. The main components of a parking pawl mechanism are the parking gear, parking pawl, actuator rod, cam collar, cam plate, pivot pin, and parking pawl return spring. The mechanism assembly is designed so that the parking pawl tooth collides and overrides the parking gear teeth (ratchets) until a safe engagement speed for the vehicle is reached. Software controls are put in place to avoid this condition and engage the pawl only when the vehicle has come to a standstill.[2]
Applicable standards
FMVSS 114 – Theft Protection and Rollaway Prevention, Keyless Ignition Systems
SAE J2208 – Park Standard for Automatic Transmissions.
Recommendations
Most vehicle manufacturers[3] and auto mechanics[4] 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 not only requires removing the transmission from the vehicle, but it's usually the first component to be installed in the gearbox case during a complete rebuild.
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.
^Jeyakumaran, Jeku; Zhang, Nong (2008). "Dynamic Analysis of an Automatic Transmission Parking Mechanism". University of Adelaide, Australia.(subscription required)
^"Chevy Cruze Owner's Manual" 2013-12-20 at the Wayback Machine. Chevrolet.com.
^"Driver's Ed Guru - Always set the parking brake". DriverSEdGuru.com
December 26, 2022
parking, pawl, parking, pawl, device, fitted, motor, vehicle, automatic, transmission, that, locks, transmission, when, transmission, shift, lever, selector, placed, park, position, park, first, position, lever, topmost, column, shift, frontmost, floor, shift,. A parking pawl is a device fitted to a motor vehicle s automatic transmission that locks up the transmission when the transmission shift lever selector is placed in the Park position Park is the first position of the lever topmost on a column shift frontmost on a floor shift in all cars sold in the United States since 1965 when the order was standardised by the Society of Automotive Engineers SAE through SAE J915 1 and in most other vehicles worldwide Interior of an automatic transmission showing the toothed locking wheel and the pawl below it a finger is touching the pawl Contents 1 Design and operation 1 1 Applicable standards 2 Recommendations 3 See also 4 External links 5 ReferencesDesign and operation EditThe 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 The main components of a parking pawl mechanism are the parking gear parking pawl actuator rod cam collar cam plate pivot pin and parking pawl return spring The mechanism assembly is designed so that the parking pawl tooth collides and overrides the parking gear teeth ratchets until a safe engagement speed for the vehicle is reached Software controls are put in place to avoid this condition and engage the pawl only when the vehicle has come to a standstill 2 Applicable standards Edit FMVSS 114 Theft Protection and Rollaway Prevention Keyless Ignition Systems SAE J2208 Park Standard for Automatic Transmissions Recommendations EditMost vehicle manufacturers 3 and auto mechanics 4 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 not only requires removing the transmission from the vehicle but it s usually the first component to be installed in the gearbox case during a complete rebuild 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 See also EditElectronic parking brake Park by wire Transmission brakeExternal links EditAutomatic transmission parking pawl for the 2004 Subaru Impreza Design Requirements for Parking Pawl Video of Parking Pawl in an automatic transmissionReferences Edit SAE International Jeyakumaran Jeku Zhang Nong 2008 Dynamic Analysis of an Automatic Transmission Parking Mechanism University of Adelaide Australia subscription required Chevy Cruze Owner s Manual Archived 2013 12 20 at the Wayback Machine Chevrolet com Driver s Ed Guru Always set the parking brake DriverSEdGuru com Retrieved from https en wikipedia org w index php title Parking pawl amp oldid 1047660459, wikipedia, wiki, book, books, library,
