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GENERAL INFORMATION
WARNING
Exceeding these ratings by
overloading can cause component
failure resulting in property damage,
personal injury or death. Fluid Temperature
If the operating temperature exceeds
250°F (121°C), the rate of axle lubrication
oxidation increases and shortens the life
of the lubricant and seals, requiring axle
lubrication changes to become more
frequent to preserve the axle. Do not
consistently run extreme pressure (EP)
lubricants above
250°F (121°C).
Axle Conversions WARNING
When operating a loaded vehicle, the
driver must keep all adjustable axles
on the ground at all times, supporting
their share of the vehicle ’s load. Failure to
do so can overload other axles, tires,
wheels, springs, steering components,
brakes and frames, resulting in early
component failure, loss of vehicle control,
possible property damage and personal
injury. We do not recommend, or approve,
performing axle conversions. However, we
understand that, on occasion, others install
aftermarket add-on axles on the truck
chassis that allow operator control for
weight transfer from other axles (such as
air lift axles). LIMITED SLIP DIFFERENTIAL WARNING
If both wheels are not raised off the
ground, the one wheel that is not
raised may pull the vehicle off its
support, possibly resulting in personal
injury. This axle provides added traction on
slippery surfaces, particularly when one
wheel is on a poor traction surface. Under
normal conditions, the limited-slip axle
functions like a standard rear axle. The axle
may exhibit a slight noise or vibration
during tight turns with low vehicle speed.
This is normal behavior and indicates the
axle is working.
Both wheels must be raised off the ground
should it be necessary to operate one
wheel with your vehicle stationary.
ELECTRONIC LOCKING
DIFFERENTIAL
Driver-Controlled Locking
Differential
Note:
Never use the differential lock at
vehicle speeds above
25 mph (40 km/h).
Some drive axles have a driver-controlled
differential lock. The differential lock can
lock or unlock the differential when your
vehicle is moving or stopped. When extra
traction is required, the differential lock
provides full power to both wheels.
When you lock the differential, your
vehicle ’s turning radius increases
(under-steer).
Take care to avoid sudden accelerations
when both drive wheels are on a slippery
surface.
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WARNING
Sudden accelerations on slippery
surfaces could cause the wheels to
spin, the vehicle to turn sideways on
a crowned road surface or in a turn,
possibly resulting in loss of vehicle control
and personal injury. Activating the Locking Differential
You can lock and unlock the differential
when your vehicle is moving at a constant
speed of less than 25 mph (40 km/h) and
while the wheels are not slipping. Do not
lock the differential when your vehicle is
traveling down steep grades and when
traction is minimal.
The differential lock and differential lock
light automatically disengage at speeds
above 25 mph (40 km/h). The differential
lock remains off until either you restart your
vehicle or you turn the differential lock
switch off then back on.
Servicing a Vehicle with a Locking
Differential
Turn the engine off and raise all drive
wheels of the locker differential axle in
order to prevent your vehicle from moving
when servicing the wheels, tires or brakes.
Axles equipped with a driver-controlled
differential deliver power to both wheels
even when only one wheel is on the ground. WARNING
Failure to raise all drive wheels with
this type of differential could cause
the vehicle to move unexpectedly,
resulting in property damage, personal
injury or death. 2-SPEED REAR AXLE
(If Equipped)
WARNING
Never shift a two-speed axle when
descending a steep grade as this
may cause loss of vehicle control and
result in personal injury. Note:
Do not shift between ranges when
the speed control is on.
A two-speed rear axle allows the driver to
select a low range for greater pulling power
and a high range for greater road speed
and fuel economy. You can also use these
ranges to provide extra steps between
transmission shifts when driving on steep
grades or fuel economy may be factors.
Axle Shifting Note:
Do not shift the axle to LOW when
your vehicle is moving. Use LOW when you
drive a fully loaded vehicle on a severe grade
or in congested traffic. Use HIGH for all
normal driving conditions with a lightly
loaded or partially loaded vehicle.
Note: The axle is set to HIGH by default.
To shift the axle between HIGH and LOW
with the vehicle stopped, place the
transmission in position N, then press and
hold the button for two seconds.
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GENERAL INFORMATION
WARNINGS
Do not drive with your foot resting on
the brake pedal. This results in
abnormally high brake temperatures,
excessive lining wear and increased
stopping distance. Continuous application of the brakes
causes the brakes to overheat,
resulting in temporary loss of braking.
Note:
Occasional brake noise is normal. If
a metal-to-metal, continuous grinding or
continuous squeal sound is present, the
brake linings may be worn-out. Have the
system checked by an authorized dealer. If
your vehicle has continuous vibration or
shudder in the steering wheel while braking,
have it checked by an authorized dealer.
All standard equipment brakes are
self-adjusting. Automatic adjustment,
when required, occurs whenever you apply
and release the brakes during forward or
reverse operation.
Know the required stopping distances for
all driving conditions you may encounter.
For longer brake lining life, take full
advantage of engine braking power when
coming to a stop. See Warning Lamps and
Indicators (page 58).
Wet brakes result in reduced braking
efficiency. Gently press the brake pedal a
few times when driving from a car wash or
standing water to dry the brakes.
If brakes do not grip well:
• Check brake adjustment.
• Check brake linings for excessive wear.
• Check system air pressure on vehicle
equipped with air brakes. •
Let the brakes cool if you have been
using them excessively, as in mountain
driving or after several fast, high-speed
stops.
• If you have been driving through deep
water, gently apply the brakes several
times while your vehicle is moving
slowly.
Anti-lock Brake System
This system helps you maintain steering
control during emergency stops by keeping
the brakes from locking. This lamp momentarily
illuminates when you turn the
ignition on. If the light does not
illuminate during start up, remains on or
flashes, the system may be disabled. Have
the system checked by an authorized
dealer. If the system is disabled, normal
braking is still effective. If the
brake warning lamp illuminates
when you release the parking brake, have
the system checked by an authorized
dealer. If you connect a PLC trailer with
the ignition on, the trailer ABS
light also illuminates. If the light
fails to illuminate, if it remains on after you
start the vehicle or continues to flash, have
the system serviced immediately.
HINTS ON DRIVING WITH
ANTI-LOCK BRAKES
Note: When the system is operating, the
brake pedal may pulse and may travel
further. Maintain pressure on the brake
pedal. You may also hear a noise from the
system. This is normal.
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The anti-lock braking system will not
eliminate the risks when:
•
You drive too closely to the vehicle in
front of you.
• Your vehicle is hydroplaning.
• You take corners too fast.
• The road surface is poor.
PARKING BRAKE
Hydraulic Brakes WARNINGS
Do not use the gearshift selector in
place of the parking brake. Always
set the parking brake fully AND make
sure the transmission is in park (P) or
neutral (N). Use of wheel chocks is also
recommended in hilly or off-road usage.
Unexpected and possible sudden vehicle
movement may occur if these precautions
are not taken. If the parking brake is fully released
but the parking brake warning lamp
remains illuminated, the brakes may
not be working properly. See your dealer
or a qualified service technician. Apply the parking brake whenever the
vehicle is parked. To set the parking brake,
pull the handle up until it snaps into the
locked position.
When the parking brake is out of
adjustment, seek service immediately.
The parking brake warning lamp
in the instrument cluster
illuminates, and remains
illuminated (when you switch on the
ignition), until you release the parking
brake. Push the palm release lever (A) on the
parking brake handle (B) and push down
as far as possible to release the brake.
Driving with the parking brake on causes
the brakes to wear out quickly and reduces
fuel economy.
We recommend you not use the parking
brake to stop a moving vehicle. However,
if the normal brakes fail, you can use the
parking brake to stop your vehicle in an
emergency. Since the parking brake only
applies retardation to the rear wheels, the
vehicle's stopping distance increases
greatly and the handling of your vehicle is
adversely affected.
Applying the Parking Brake
Note:
If the light blinks and a warning tone
sounds when you pull the control knob, the
parking brake is not functioning properly.
Seek immediate service from your dealer.
Pull the yellow, dash-mounted parking
brake knob. The parking brake light
illuminates indicating that the parking
brake has been successfully set.
Releasing the Parking Brake WARNING
Hold the brake pedal down while
moving the gearshift lever from
position to position. If the brake
pedal is not held down, the vehicle may
move unexpectedly resulting in property
damage, personal injury or death. 121
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Note:
Read and understand the following
steps and perform them whenever you
prepare to drive the vehicle.
Note: The parking brake does not disengage
unless sufficient system air pressure is
available.
1. Press and hold the service brake pedal
while the engine is running.
2. Select the appropriate drive gear.
3. Push and hold the yellow dash-mounted parking brake knob until
the parking brake light turns off, then
release.
Parking Brake Light Illumination due
to Low Air Pressure
If the air pressure becomes too low at any
time during vehicle operation, the parking
brake may apply and the parking brake
light turns on.
If the parking brake applies due to low air
pressure, immediate service is required to
the parking brake system.
Parking Brake Warning System
If the parking brake light blinks and a tone
sounds when pulling the yellow control
knob out, this indicates the parking brake
is not functioning properly. Seek service for
the parking brake immediately.
With the ignition key not in the run position:
• A tone sounds if the parking brake
remains released (or in an unknown
state). The tone stops after
approximately 8 minutes or until the
parking brake is applied. Seek service
for the parking brake immediately. Diesel engines: Parking brake light
operation (the light only works when the
ignition key is in the run position):
• On:
Parking brake applied.
• Off:
Parking brake released and no
faults or malfunctions detected.
• Blink and tone:
Parking brake
released (or in an unknown state) and
faults or malfunctions detected.
Releasing Spring Manually WARNINGS
Do not attempt to disassemble the
parking brake chamber under any
circumstances. The high spring load
may cause serious injury. Block the wheels to help prevent the
vehicle from moving.
Unexpected and possibly sudden
vehicle movement may occur if these
precautions are not taken.
If you release hydraulic pressure from the
spring brake chamber the power spring
applies the brake and, unless hydraulic
pressure can be re-established, you must
release the spring brake as follows in order
to move your vehicle.
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Loosen the jam nut (A) and un-thread the
adjustment rod (B) from the chamber to
reduce tension on the cable (C). Continue
to un-thread the adjustment rod all the
way and remove it from the chamber.
Air Brakes
WARNING
This control is used for parking only.
Do not leave the vehicle unattended
after setting the parking brake
without placing the transmission park (P).
Use of wheel chocks is also recommended
in hilly or off-road usage. If the service brakes should fail to operate
while your vehicle is moving, you can make
an emergency stop with the parking brake.
Since the parking brake only applies
stopping power to the rear wheels, your
vehicle
’s stopping distance greatly
increases and the handling of your vehicle
is adversely affected. Make repairs
immediately to an inoperative air brake
system circuit. Pull the yellow parking brake knob out to
apply the parking brake. Push the knob in
to release the parking brake.
The parking brake light
illuminates and remains
illuminated (when you switch
the ignition to the on position) until you
release the parking brake. Releasing Spring Brake with Air
Pressure
The air system in all vehicles with
spring-actuated rear wheel parking brakes
is equipped with a valve located on the
governor for connection to an outside air
supply. The valve lets you recharge the
system with air from an outside source,
releasing the spring-actuated parking
brakes. Your vehicle is now ready to tow in
an emergency.
You can only use an outside air source if
the protected system is in operating
condition. If you cannot restore air pressure
in the protected air system, you must
release the spring-actuated brakes
manually.
Releasing Spring Manually
WARNINGS
Do not attempt to disassemble the
parking brake chamber under any
circumstances. The high spring load
may cause serious injury if the chamber
clamps are removed. Block the wheels to help prevent the
vehicle from moving.
Unexpected and possibly sudden
vehicle movement may occur if these
precautions are not taken.
If you release air pressure from the spring
brake chamber, the power spring applies
the brake and, unless air pressure can be
re-established, you must release the spring
brake as follows in order to move your
vehicle.
Do not use impact wrenches as they may
damage the piston and prevent proper
caging of the spring. Do not apply more
than 50 lb.ft (68 Nm) to the release bolt
nut.
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1.
Remove the stud tool and nut from the
carrying pocket on the brake chamber
assembly. 2. Remove the access plug from the end
of the spring chamber.
3. Insert the release stud through the opening in the chamber and into the
spring pressure plate. 4.
Turn the release stud ¼ turn to engage
the stud tangs with the slot in the
pressure plate. Keep the stud engaged
and install the nut on the release stud.
5. Tighten the nut until the spring is fully caged and brakes released. Do not
loosen or remove the release stud and
nut unless you completely assemble
and securely clamp the brake chamber.
6. After restoring the air pressure, unscrew and remove the release stud
and install in the carrying pocket. Install
the access plug. FULL POWER BRAKE WARNING
If the brake warning lamp in the
instrument cluster remains
illuminated after engine start up, this
indicates a system failure in the Full Power
Brake system. Stop the vehicle safely as
soon as possible and seek service
immediately. This system incorporates standard braking,
an anti-lock braking system (ABS) and
optional Power Park Brake into one fully
integrated hydraulic brake system. With
the Full Power Brake system, braking
energy is stored, similar to an air brake
system, resulting in faster response times
and shorter stopping distances. This is
accomplished using motor and pump
assemblies that pressurize the system by
pumping brake fluid into accumulators.
This is similar to the air compressor of an
air brake system pressurizing the air tanks.
The system includes a master cylinder that
provides the normal pedal feel and
transfers the pedal force, via brake fluid,
to the main components of the system.
Note:
The motor and pumps run
momentarily with the ignition switch in the
on or run position, or in the off position with
the brake pedal pressed.
Note: During normal driving, you may hear
the pump and motors replenishing the
accumulators. This is a normal function of
the system.
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AIR BRAKES
WARNINGS
Do not drive or continue to drive if the
low air pressure buzzer is sounding
or the brake warning light is lit. These
warnings indicate that air pressure is not
to normal operating level. Continued use
of the vehicle could result in loss of braking
ability. Avoid repeated light application of
the brake pedal. This depletes air
pressure faster and could result in
loss of braking capability. Do not move the vehicle when the
air pressure is insufficient because
the brake system may be inoperative.
After starting the engine, give the air
compressor time to build up the air
pressure to 60 psi (414 kPa) before moving
your vehicle. Periodically check the air pressure gauge
while driving. Pressure should range
between approximately 100 psi (690 kPa)
to
130 psi (896 kPa). The air compressor
governor cut-in and cutout pressure
settings are set at the factory and are not
adjustable. When air pressure is insufficient
(below
60 psi (414 kPa)), a
warning light illuminates and a
buzzer sounds when the ignition is in the
on position. This may happen because
excessive brake applications are depleting
the system air pressure. If this condition
occurs, stop driving your vehicle until the
compressor has fully recharged the air
system.
Select a gear ratio to help slow your vehicle
before descending grades. Supplementing
with brakes, as required, help to safely slow
the vehicle and avoids overspeeding the
engine.
Air Chamber Stroke Indication
Air chamber push rods have orange stroke
indicator markers that warn when the
braking system requires adjustment or
repair. The painted orange indicator is on
the air chamber push rod at the slack
adjuster stroke dimension that requires
service when visible during brake
application.
A qualified service technician should
perform air brake inspection and
adjustment or repairs keeping to the
instructions in the service manual.
Cam Brakes - Automatic Slack
Adjusters WARNING
Do not manually adjust the
automatic slack adjusters to correct
excessive push rod stroke as it may
result in reduced brake effectiveness and
a vehicle crash. Excessive push rod stroke
indicates that a problem exists with the
automatic adjuster, with the installation
of the adjuster, or with foundation brake
components that manual adjustment does
not remedy. Seek service from a qualified
facility for excessive push rod stroke. 125
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