Spicer Tandem Drive Axles Service Manual D__R440, 460, 480, D_R461, 462, 463, 521, 581, 601, 651, 652, 653 - Manual (Page 135)

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Theory of Operation
Theor
y of Operation
Torque Distribution with Lockout Engaged
(Inter-axle Differential is Not Operating)
A lockout mechanism is incorporated in the power divider to
enable the vehicle driver to lock out the inter-axle differential
and provide maximum traction under adverse road conditions.
In operation, an air cylinder (controlled by a cab-mounted
valve) shifts a sliding clutch on the input shaft. To lock out in-
ter-axle differential action, the clutch engages the helical-side
gear and causes this gear, the input shaft and differential to ro-
tate as one assembly. This action provides a positive drive to
both axles. The clutch should only be engaged when both axles
are rotating at the same speed. Operation should be limited to
low traction situations and should be disengaged when normal
traction returns. Failure to do so will result in poor handling
and damage to the axle components.
With the lockout engaged, torque is distributed to both axles
without differential action. The forward axle pinion and ring
gear are driven by the helical side gear. The rear axle gearing
is driven from the output shaft side gear and inter-axle drive-
line.
Note: Varied road surface conditions can result in unequal
torque distribution between the two axle assemblies.
Prolonged operation with the lockout engaged can damage
axle and driveline components.
CAUTION
1 - Input torque
2 - Drive is from input shaft through helical gears to forward gearing
3 - Drive is from output shaft side gear to rear gearing
4 - Inter-axle differential not operating
5 - Lockout engaged
1
5
2
3
4
Torque is transmitted to both axles without inter-axle differential action