Spicer Tandem Drive Axles Service Manual D__R440, 460, 480, D_R461, 462, 463, 521, 581, 601, 651, 652, 653 - Manual (Page 121)

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Dual Range Axle Shift Systems
Dual Range Axle Shift
S
ystems
Axle Range Selection and Inter-Axle
Differential Lockout System
Description and Operation
The Axle Range Interlock feature in this system is designed to
prevent axle shifting when the inter-axle differential is locked
out (or when lockout is engaged). The basic shift system operates the same as the standard shift
system to shift axle and engage or disengage lockout. Howev-
er, it varies by adding an Interlock Pin Assembly to the axle
range shifter valve and an Interlock Control Valve to the lockout
cylinder. These two components are interconnected with air-
lines (see illustration above). In operation, the Interlock Pin As-
sembly blocks movement of the axle range shifter valve lever
when air pressure is present. Refer to the following page for
operation description.
1 - Circuit breaker †‡
2 - Speedometer adapter †
3 - Air pressure
4 - Interlock pin assembly (mounted in
cover) (blocks lever with lockout en-
gaged)
5 - Axle range shifter valve (open in high
range)
6 - Solenoid valve ‡ (exhaust system
when de-energized)
7 - Inter-axle differential lockout shifter
valve (open in “lock” position)
8- Air pressure 9 - Interlock control valve (open when
lockout is engaged)
10 - Air pressure with axle in high range,
inter-axle differential engaged, and axle
shifter valve lever blocked.
11 - Inter-axle differential lockout cylin-
der
12 - Rear axle shift unit
13 - Ignition switch †‡
14 - Pressure switch † (normally closed)
15 - Quick release valve
16 - Exhaust
17 - Dry air tank
18 - Forward axle shift unit † Pressure switch and speedometer
adapter required for vehicles with trans-
mission drive speedometers.
‡ Solenoid valve required for vehicles not
equipped with automatic safety brakes.