Service Manual D__R440, 460, 480, D_R461, 462, 463, 521, 581, 601, 651, 652, 653 Owner manual

111
Control Systems
Control Systems
Control Systems
Two types of systems may be used to control the Differential
Lock operation:
• Transmission low-range interlock control system
• Direct driver-controlled system
Note: The interlock system is preferred for vehicles equipped
with an air-shifted, low-range transmission. It is de-
signed to insure the differential lock is not left engaged
(and to prevent accidental engagement) when transmis-
sion is in high range.
Transmission Low Range Interlock Control System
(preferred system)
The wheel differential is locked manually with the transmission
in low range. It is unlocked by the driver or unlocked when the
transmission is shifted out of low range.
With this system, the wheel differential lock can only be en-
gaged when the transmission is in low range. Operation is as
follows:
1. When the transmission is in a range above low speed,
the transmission low range control valve is closed
shutting off air supply to the cab-mounted control
valve and differential lock shift units. The differential
lock is disengaged and the wheel differential func-
tions normally.
2. With the transmission in low-range, the transmission
control valve opens and supplies pressure to the cab
mounted control valve.
3. When the driver places the cab-mounted control
valve in the lock position and with the assist pressure
from the transmission control circuit, tank air pres-
sure is supplied to the differential lock shift units
through the cab-mounted control valve. The shift fork
is moved to engage the sliding curvic clutch with the
flanged half differential case.
4. When the control switch is placed in the unlock posi-
tion, air pressure supply to the shift unit is shut off
and air pressure is released from the shift unit. A
compression spring moves the shift fork to disen-
gage the sliding clutch from the flanged case half un-
locking the wheel differential.
Note: If the transmission is shifted out of low-range (with cab
mounted control valve in the lock position), the air pres-
sure to the differential shift units is shut off automatical-
ly. The transmission low range valve closes, shuts off air
assist supply to the cab mounted control valve which, in
turn, releases the tank air pressure from the air shift
units.
If the driver subsequently shifts back into low range, the differ-
ential lock will not re-engage automatically.
Note: With either control system, torque on the wheel differen-
tial must be relieved to allow the differential to fully lock
or unlock. Press clutch.
1 - Quick release valve
2 - Transmission
3 - Rear axle wheel differential lock air shift unit
4 - Fuse or circuit breaker
5 - Fuse or circuit breaker
6 - Indicator light or audible signal
7 - Wheel differential lock selector switch
8 - Exhaust
9 - Wheel differential lock selector switch
10 - Indicator light or audible signal
11 - Power supply
8
9
1
10
6
5
3
11
2
7
4
• Engage only when traction is poor.
WARNING
!
This vehicle is equipped with the
Spicer Driver Controlled Wheel
Differential Lock.
For further information
consult your owners manual
[publication #XX-XXXX]
Steering will be adversely
affected when engaged.
• Do not engage when tires are spinning.
• Disengage when going downhill.
DRIVE CAREFULLY
WHEN ENGAGED
• Disengage at speeds above 25 mph.
Disengaged
Engaged