Trouble shooting – Spicer Tandem Drive Axle Dual Range & Double Planetary 34,000-45,000 lbs User 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

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.

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.

Move axle shifter valve lever to Low

Range. In this position, air pressure

should be present only up to axle

shifter valve.

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.

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

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.

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

Make sure adapter is grounded to

vehicle chassis.

Check wiring for shorts or grounds

and trace electrical circuit from igni-

tion switch through circuit breaker,

pressure switch to adapter.

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.