Spicer Tandem Drive Axles Service Manual D__R440, 460, 480, D_R461, 462, 463, 521, 581, 601, 651, 652, 653 - Manual (Page 119)

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Dual Range Axle Shift Systems
Dual Range Axle Shift
S
ystems
For vehicles equipped with transmission-drive speedometers,
the system includes a speedometer adapter which compen-
sates speedometer readings when axle is in Low Range. The
adapter is operated by an electrical switch mounted on or near
the quick-release valve. The switch is normally-closed and is
opened by air pressure.
With axles in Low Range, the switch is closed and the adapter
is energized. The adapter operates with a ratio compatible with
the axle Low Range for proper speed readings. With axle in
High Range, the airlines are pressurized and the pressure
switch is open. The adapter now operates with 1:1 ratio for
proper speed readings in High Range.
Axle Shift System Operation High Range
When shifter valve is moved to the High position, the valve is
opened and air pressure is supplied through the quick release
valve to both axle shift units. When driveline torque is inter-
rupted, the shift units will shift both axles to High Range.
Low Range
When shifter valve is moved to the Low position, the valve is
closed. Air pressure in the shift units is exhausted through the
quick release valve. When driveline torque is interrupted, both
axles are shifted to Low Range and held in this position by shift
unit return springs.
Inter-Axle Differential Lockout System
The lockout air shift system consists of:
1. A manually-operated air shifter valve which controls
engagement or disengagement of the inter-axle dif-
ferential.
2. A lockout cylinder which operates under air pressure.
This cylinder is mechanically-connected to a shift-
fork and sliding clutch. The clutch engages or disen-
gages a differential helical-side gear to “Lock” or
“Unlock” the differential.
Lockout System Operation
For operation description, refer to the following page.