Ford F-650 2015 Owner's Manual page 154

If you release hydraulic pressure from the spring brake chamber the
power spring applies the brake and, unless hydraulic pressure can be
re-established, you must release the spring brake as follows in order to
move your vehicle.
Loosen the jam nut (A) and un-thread the adjustment rod (B) from the
chamber to reduce tension on the cable (C). Continue to un-thread the
adjustment rod all the way and remove it from the chamber. The nut and
shaft are metric.
Air Brakes
WARNING: Do not use the gearshift selector in place of the
parking brake; unexpected and possible sudden vehicle
movement may occur if these precautions are not taken. Always set the
parking brake fully AND make sure the gearshift selector is in position
R for vehicles equipped with manual transmission or position N (except
Allison 2200 transmission) or P (Allison 2200 transmission) for vehicles
with automatic transmission.
If the service brakes should fail to operate while your vehicle is moving,
you can make an emergency stop with the parking brake. Since the
parking brake only applies stopping power to the rear wheels, your
vehicle's stopping distance greatly increases and the handling of your
vehicle is adversely affected. Make repairs immediately to an inoperative
air brake system circuit.
2015 F-650/750 (f67)
Owners Guide gf, 2nd Printing, April 2014
USA (fus)
Brakes
C
A
B
153