Spicer Drive Axles Service Manual Axle Shift Systems, 2-Speed Single Rear Axles - Manual (Page 22)

19
Air Shift System
Air Shift System
Description
The basic system consists of:
1. A 2-position manually operated air shifter valve.
2. A quick release valve.
3. An air shift unit.
The system operates at reservoir tank air pressure.
For vehicles not equipped with automatic safety brakes, an
ignition-controlled solenoid valve exhausts the system and
down-shifts axle when ignition switch is turned off. The elec-
trical circuit is protected by a circuit breaker.
For vehicles equipped with transmission drive speedome-
ter, the system includes a speedometer adapter. Operation is
controlled by an electric switch (normally closed—opened by
air pressure). This switch is mounted on or near the quick
release valve.
Operation
In operation, the air shifter valve (in gear shift knob) supplies
air through the quick release valve to the axle shift unit. Air
pressure in the shift unit shifts axle to High range. To shift
axle to Low range, air pressure is exhausted at shifter valve,
which exhausts air pressure at quick release valve, allowing
shift unit to return to Low range.
Low Range Operation — Shifter knob is in “LO”, shifter valve
is closed and no air pressure is present to shift unit. Axle is
held in Low range by shift unit return spring.
High Range Operation — Shifter knob is in “HI”, shifter valve
is opened to allow air pressure through quick release valve to
shift unit. Axle is held in High range by air pressure in the shift
unit.
Axle Shift Unit
Quick Release Valve
Exhaust
Dry Air Tank
+Speedometer Adapter
2-Speed Air
Shifter Valve
* For Vehicles
Not Equipped with
Automatic Safety Brakes
+ For Vehicles with
Transmission Drive
Speedometers
White
Red
Green
Exhaust
* Ignition or
Accessory Switch
* Circuit
Breaker
+ Pressure Switch
(normally closed)
* Solenoid Valve