Parking Brake and Speed Shift
(1) Sped selection switch. (2) Parking brake button.
Parking Brake And Speed Shift Control Valve.
(3) Parking brake solenoid. (4) Speed shift solenoid. (5) Parking
brake valve. (6) Speed shift control valve.
Parking Brake Valve
Parking brake valve (5) is a solenoid operated, two position
valve that controls the operation of the brake in the drum drive
When parking brake button (2) is pushed in (parking brake
applied), parking brake solenoid (3) is not energized. The
valve in this position allows the oil from the brake release
piston to drain through the thermal bypass valve and on to the
tank and the brake springs will apply the parking brake.
When the button is pulled out (parking brake released), parking
brake solenoid (3) is energized. The parking brake valve in
this position allows unfiltered charge oil to go to the piston of
the brake and will release the parking brake.
Speed Shift Control Valve
Speed shift control valve (6) is a solenoid operated, two
position valve that controls the operation of the speed shift
mechanism in the drum and axle propel motors.
When speed selection switch (1) is in the LOW speed position,
speed shift solenoid (4) is not energized. The control vale in
this position allows oil from the shift valves and the motors to
go to the thermal bypass valve. The motors are now in the
maximum displacement position (LOW speed).
When the speed selection switch is in the HIGH speed
position, speed shift solenoid (4) is energized. The speed shift
control valve in this position allows unfiltered charge oil from
the steering pump to go to the shift valves in the motors. The
motors are now in the minimum displacement position (HIGH