Spicer Convertible Tandem Axles - Manual (Page 68)

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Theory of Operation
Differential Lock Engaged
Air pressure applied to the shift cylinder moves the piston,
push rod, shift fork and the sliding curvic clutch engages the
fixed curvic clutch.
The sliding clutch is splined to the axle shaft. The fixed clutch
is splined to the differential case hub. Engaging the two
clutches locks the wheel differential thus preventing wheel dif-
ferential action.
Differential Lock Disengaged
When air pressure at the shift cylinder is released, a compres-
sion spring (mounted on the push rod) moves the push rod,
shift fork and sliding clutch as an assembly. The sliding clutch
moves out of engagement with the fixed clutch. The wheel dif-
ferential is unlocked and operates normally.
Differential Lock Engagement Indicator
Differential lock engagement is detected by a switch (electric)
mounted on the differential carrier. An actuator, mounted in
the piston cover, operates the switch.
When the shift fork moves to engage the differential lock, the
push rod actuator moves away from the switch, allows the
switch to close and send an electrical signal to turn on a cab-
mounted indicator light (or an audible signal).
When the shift fork moves to disengage the differential lock,
the compression spring also moves the push rod actuator to
contact the switch. The switch is opened and turns off the
cab-mounted indicator light (or the audible signal).
Differential Lock Engaged
1 - Spring is compressed
2 - Shift fork
3 - Piston and rod
4 - Selector switch
5 - Air pressure applied engages clutches
6 - Fixed clutch splined to differential case
7 - Sliding clutch splined to axle shaft and engaged with

fixed clutch
1
6
2
3
4
5
7
Differential Lock Disengaged
1 - Spring is decompressed
2 - Shift fork
3 - Piston and rod
4 - Selector switch
5 - Air pressure applied disengages clutches
6 - Fixed clutch splined to differential case
7 - Sliding clutch splined to axle shaft
1
6 7
2
3
4
5