Spicer Tandem Drive Axles Service Manual D__R440, 460, 480, D_R461, 462, 463, 521, 581, 601, 651, 652, 653 - Manual (Page 124)

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Troubleshooting
Troubleshooting
Check for Air Pressure and Air Leaks
A simple method for quickly locating troubles in a shift system
can be accomplished 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 elec-
trical 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 pressure 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 lever back
and forth from “LO” to “HI”. If the shift unit is operat-
ing, a definite reaction will be evident by sound of
parts movement.
5. If air pressure is satisfactory and shift unit does not
operate, disassemble and inspect shift unit.
Check Pressure Switch
In Low Range, the pressure switch is closed and electrical cir-
cuit is complete 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” position, 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 connection, 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 lock-
out and interlock system. Check for air leaks with lockout en-
gaged. Repair leaks.
Note: If lockout will not engage with air pressure present at
cylinder cover side connection, remove and check cylin-
der.
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 connection. Check valve operation in both lockout
positions. If valve operation 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 pressure should op-
erate locking pin to block movement of the axle shifter valve le-
ver.
To check operation, move the lockout 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.