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The parking-brake mechanism engages the teeth on the output to hold the car still. This is the section of the transmission that hooks up to the drive shaft – so if this part can't spin, the car can't move.
The output of the transmission: The square notches are en- gaged by the parking-brake mechanism to hold the car still.  
The empty housing of the transmission with the parking brake mechanism poking through, as it does when the car is in park.
At the right you see the parking mechanism pro- truding into the housing where the gears are located. Notice that it has tapered sides. This helps to disen- gage the parking brake when you are parked on a hill – the force from the weight of the car helps to push the parking mechanism out of place because of the angle of the taper.
AUTOMATIC TRANSMISSIONS
APRIL 2018