Spicer Tandem Drive Axle Dual Range & Double Planetary 34,000-45,000 lbs - Manual (Page 64)

Trouble Shooting
Check for Air Pressure and
Air Leaks
A simple method for quickly locating
troubles in a shift system can be accom-
plished by listening for possible air
leaks and for sound which would
indicate mechanical shifting.
Axle Shift System
1.
When system includes a solenoid
valve, turn ignition “ON” to energize
and open the solenoid valve.
If electrical system is functioning, air
pressure should be present at valve
outlet connection.
2.
Move axle shifter valve lever to
High Range. In this position, air pres-
sure should be present in the entire
system. Check for air leaks.
3.
Move axle shifter valve lever to Low
Range. In this position, air pressure
should be present only up to axle
shifter valve.
4.
To check axle for shifting, operate
shifter Iever back and forth from “LO”
to “HI”. If the shift unit is operating, a
definite reaction will be evident by
sound of parts movement.
5.
If air pressure is satisfactory and
shift unit does not operate, disassem-
ble and inspect shift unit.
Check Pressure Switch.
In Low Range, the pressure switch is
closed and electrical circuit is com-
plete to the speedometer adapter. In
High Range, air pressure opens the
pressure switch, breaks the electric
circuit to the speedometer adapter.
To check pressure switch operation,
shift to High Range and probe switch
terminals. No voltage should be
present. Replace a faulty pressure
switch as an assembly.
Check Quick Release Valve.
The quick release valve provides a
means of quickly exhausting air from
system when axle is shifted from High
to Low Range.
To check valve operation, listen for
audible air exhaust from valve when
shifting axle from High to Low Range.
Replace a faulty quick release valve
as an assembly.
Check Lockout (standard).
With shifter valve in the “Lock” posi-
tion, air pressure is present in the
entire lockout system. Check for air
leaks with lockout engaged. Repair
leaks.
NOTE:
If lockout will not engage with
air pressure present at cover connec-
tion, remove and check lockout
cylinder.
Check Lockout (with axle
range interlock).
With shifter valve in “Lock” position,
lockout is engaged and air pressure
is present in all lines and components
of the lockout and interlock system.
Check for air leaks with lockout
engaged. Repair leaks.
If lockout will not engage with air
pressure present at cylinder cover
side connection, remove and check
cylinder.
Check Interlock Control Valve
Air pressure is present at the
inlet connection at all times.
With lockout engaged, the valve
should open and air pressure
should be present at the valve
side connection.
With lockout disengaged, valve
should be closed, blocking air
at the side connecton.
Check valve operation in both
lockout positions. If valve oper-
ation is faulty, replace the
assembly.
Check Interlock Pin Assembly
Air pressure is present at the axle
range shifter valve cover connection
when lockout is engaged. Air pres-
sure should operate locking pin to
block movement of the axle shifter
valve lever.
To check operation, move the lock-
out shifter lever to the “Lock” position.
If lever operation is not blocked,
check for air pressure at the Interlock
Pin connection. If air pressure is
present, repair Interlock Pin Assembly.
Check Electrical System
Check Solenoid Valve
1.
When ignition switch is "ON";
solenoid valve is energized and air
pressure is available to operate the
system. When ignition switch is “OFF;
solenoid valve is de-energized and
exhausts the system which down-
shifts axle to low range. Check wiring
and circuit breaker for defects that
would cause shorts or open circuits.
2.
Make sure valve has a good ground
connection to the frame. With power
at valve, check operation as follows:
Disconnect lead wire and air line
outlet at valve and install air pressure
gauge.
Apply power to valve and observe air
gauge reading. Operating pressure
should be approximate reservoir
pressure.
If gauge indicates approximate pres-
sure, valve is okay.
If gauge indicates low or no pressure,
valve is faulty. Replace valve assembly.
Check Speedometer Adapter
1.
Make sure adapter is grounded to
vehicle chassis.
2.
Check wiring for shorts or grounds
and trace electrical circuit from igni-
tion switch through circuit breaker,
pressure switch to adapter.
3.
Check for power supply at adapter
terminal. With axle shifter valve in
High Range, pressure switch is open
and power is not delivered to adapter.
With shifter valve in Low Range, the
pressure switch is closed and power
is delivered to operate the speed-
ometer adapter. If power supply is
okay, adapter is faulty. Replace
adapter assembly.
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