MikeD wrote:I haven't read any explanation of how the P position "parking lock" operates, only how the "parking brake" operates (rear drum brakes applied via two cables pulled tight by a 12 volt motor and released normally by a (the same?) 12 volt device, but optionally manually released by the brake release tool used in the cargo floor.
Can anyone link me to such an explanation?
explains the parking pawl mechanism.
MikeD wrote:I would like to fully understand the implication of the following "TRANSIT DRIVER HANDLING TIPS" statement: "When the auxiliary (12V) battery is completely discharged [and I assume the emergency brake's capacitor is also completely discharged], use chocks because both the parking lock and the parking brake cannot be enabled." I take this to mean that under certain conditions when the car is on a hill and the car is "off", only the manual foot brakes will keep the car from rolling down the hill...
During transit, if all power is absent (traction and 12V batteries both kaput), one won't be able to apply the parking brake nor put the vehicle into "park" after moving the car, so yes, chocks would be needed to immobilize the car. But if you have power and can apply the parking brake, then the parking brake alone is required to hold the vehicle stationery.
Federal Motor Vehicle Safety Standards
's standard #105, Hydraulic and electric brake systems
, require that the parking brake be frictional (S5.2
) and be able to hold the car stationery without requiring continuous electrical energy, hydraulic pressure, or air pressure (can't find the reference for this just now...), on a 20 percent grade for 5 minutes (S22.214.171.124
MikeD wrote:I expect that one should not rely upon the P position "parking lock" to hold the car, but only the "parking brake".
The Fed standards require that, with the parking brake disengaged, the parking mechanism be able to "not disengage or fracture in a manner permitting vehicle movement, when the vehicle is impacted at each end, on a level surface, by a barrier moving at 21/2mph.