Spicer Single Drive Axles Service Manual: S170, S190, S590 - Manual (Page 69)

65
Theo
ry of Operation
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 differential action.
Differential Lock Disengaged
When air pressure at the shift cylinder is released, a com-
pression spring (mounted on the push rod) moves the push
rod, shift fork and sliding clutch as an assembly. The slid-
ing clutch moves out of engagement with the fixed clutch.
The wheel differential is unlocked and operates normally.
Differential Lock Engagement Indicator
Differential lock engagement is detected by a switch (elec-
tric) 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