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).
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
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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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Rear Axle
Engine starting (with parking brake applied)
Check the gauge (diesel engine) or indicator light (gasoline
engine) to verify the alternator is charging. Voltmeter
Inspect for excessive free play in the steering linkages. The
steering wheel should have less than 2 in (5 cm) of free play
at its rim. Steering linkage free play
Verify the parking brake holds the vehicle by gently trying to
pull forward with the parking brake applied. Parking brake
Verify operation using the following procedure. Chock the
wheels, if necessary. Push in the parking brake and, on
tractors, push in the tractor parking brake knob: Air brakes
1. Verify the air compressor or governor cutout pressure is
approximately 120 psi (827 kPa).
2. Turn off the engine, and then turn the key back to the on
position (without starting the engine).
3. Without the brake pedal applied, note the air pressure drop
for one minute. It should be less than 2 psi (14 kPa) for single
vehicles and 3 psi (21 kPa) for combination vehicles.
4. Press and hold the brake pedal with 90 psi (621 kPa) or
more. Make sure there is no more than a 3 psi (21 kPa) per
minute leak for single vehicles and a 4 psi (28 kPa) minute
leak for combination vehicles.
5. Pump the brake pedal to deplete the system of air pressure.
The warning light and tone should turn on at 57 psi (393 kPa).
6. Pump the brake pedal and make sure the parking brake
and trailer parking brake knobs pop out at 20 psi (138 kPa)
or higher.
Verify that the fluid level is in the proper operating range. See
Automatic Transmission Fluid Check (page 242). Automatic transmission
fluid
Front of vehicle
Verify all exterior lights illuminate and are clean. Lights
Check headlights function on high and low beam.
Verify reflectors are clean, unbroken and of proper color (red
on rear, amber elsewhere).
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Vehicle Inspection Guide
Inspect the transmission fluid level and
shift linkage for proper operation.
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Vehicle Inspection Guide
UNDER HOOD OVERVIEW - 6.7L DIESEL
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Engine compartment fuse box. See Fuses (page 200). A
Windshield washer fluid reservoir. See Washer Fluid Check (page 249). B
Automatic transmission fluid dipstick. See Automatic Transmission Fluid
Check (page 242). C
Secondary Cooling System Reservoir. See Engine Coolant Check (page 233). D
Engine coolant reservoir. See Engine Coolant Check (page 233). E
Secondary fuel filter. See Draining the Fuel Filter Water Trap (page 232). F
Engine oil separator. See Changing the Engine Oil and Oil Filter (page 226). G
Engine oil filler cap. See Engine Oil Check (page 224). H
Brake fluid reservoir. See Brake Fluid Check (page 244). I
Power steering fluid reservoir. See Power Steering Fluid Check (page 245). J
Air brake compressor. See Brake System Inspection (page 255). K
Engine oil dipstick. See Engine Oil Dipstick (page 224). L
Air cleaner assembly. See Changing the Engine Oil and Oil Filter (page 226). M
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Maintenance
UNDER HOOD OVERVIEW - 7.3L
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Engine compartment fuse box. See Fuses (page 200). A
Engine oil dipstick. See Engine Oil Dipstick (page 224). B
Windshield washer fluid reservoir. See Washer Fluid Check (page 249). C
Automatic transmission fluid dipstick. See Automatic Transmission Fluid
Check (page 242). D
Engine coolant reservoir. See Engine Coolant Check (page 238). E
Engine oil filler cap. See Engine Oil Check (page 225). F
Brake fluid reservoir. See Brake Fluid Check (page 244). G
Power steering fluid reservoir. See Power Steering Fluid Check (page 245). H
Air cleaner assembly. See Changing the Engine Air Filter (page 230). I
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Maintenance
4. Check the coolant level. If the coolant
level is at or below the minimum mark,
add prediluted coolant immediately.
5. When the engine temperature cools,
you can re-start the engine. Have your
vehicle checked as soon as possible to
minimize engine damage.
Note: Driving your vehicle without repair
increases the chance of engine damage.
Engine Coolant Temperature
Management (If Equipped)
WARNING: To reduce the risk of
crash and injury, be prepared that the
vehicle speed may reduce and the
vehicle may not be able to accelerate
with full power until the coolant
temperature reduces.
If you tow a trailer with your vehicle, the
engine may temporarily reach a higher
temperature during severe operating
conditions, for example ascending a long
or steep grade in high ambient
temperatures.
At this time, you may notice the coolant
temperature gauge moves toward the red
zone and a message may appear in the
information display.
You may notice a reduction in vehicle
speed caused by reduced engine power in
order to manage the engine coolant
temperature. Your vehicle may enter this
mode if certain high-temperature and
high-load conditions take place. The
amount of speed reduction depends on
vehicle loading, grade and ambient
temperature. If this occurs, there is no
need to pull off the road. You can continue
to drive your vehicle.The air conditioning may turn on and off
during severe operating conditions to
protect the engine from overheating. When
the coolant temperature decreases to the
normal operating temperature, the air
conditioning turns on.
If the coolant temperature gauge moves
fully into the red zone, or if the coolant
temperature warning or service engine
soon messages appear in your information
display, do the following:
1. Pull off the road as soon as safely
possible and shift the transmission into
park (P).
2. Leave the engine running until the
coolant temperature gauge needle
returns to the normal position. After
several minutes, if the temperature
does not drop, follow the remaining
steps.
3. Switch the engine off and wait for it to
cool. Check the coolant level.
4. If the coolant level is at or below the
minimum mark, add prediluted coolant
immediately.
5. If the coolant level is normal, restart
the engine and continue.
AUTOMATIC TRANSMISSION
FLUID CHECK
The transmission does not consume fluid.
However, check the fluid level if the
transmission is not working properly, for
example if the transmission slips, shifts
slowly or if there are signs of fluid loss.
Replace the transmission fluid and filter
on your vehicle at the specified service
interval. See Scheduled Maintenance
(page 319).
Automatic transmission fluid expands
when warmed. To check the fluid level
consistently and accurately, do the
following:
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Maintenance
1. Drive the vehicle until it reaches normal
operating temperature. This may take
up to 20 mi (30 km). Make sure that
the transmission fluid temperature
gauge on the instrument cluster is
within normal operating temperature
196–215°F (91–102°C) before
checking.
2. Make sure that your vehicle is on level
ground.
3. With the engine running, parking brake
engaged and your foot on the brake
pedal, move the gearshift lever through
all of the gear ranges. Allow sufficient
time for each gear to engage.
4. Make sure the parking brake is on. Make
sure the transmission is in park (P) or
neutral (N) and leave the engine
running.
5. Open the hood. See Opening and
Closing the Hood (page 220).
6. Remove the dipstick and wipe it with
a clean, lint-free cloth. See Under
Hood Overview (page 222).
7. Replace the dipstick and remove it
again to check the fluid level.
8. If the fluid level is correct, replace the
dipstick and make sure it is fully seated.
Note:If the fluid level is between the
maximum and minimum marks, the fluid
level is acceptable. Do not add fluid.Transmission Fluid Level
Low Fluid Level
E163740
If the fluid level is at or below the minimum
mark, add fluid immediately. See
Automatic Transmission Fluid
Capacity and Specification (page 302).
Note:If there is no indication of fluid on the
dipstick, have your vehicle checked
immediately.
Correct Fluid Level
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Make sure that the fluid level is between
the maximum and minimum marks.
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Maintenance
High Fluid Level
E163744
Do not add fluid further than the maximum
mark. Fluid levels above the maximum
mark could cause shift or engagement
concerns and possible damage.
Note:An overheating condition can cause
high fluid levels.
Adding Transmission Fluid
Do not use supplemental transmission
fluid additives, treatments or cleaning
agents. The use of these materials could
affect transmission operation and result
in damage to internal transmission
components and could lead to
transmission damage that the vehicle
Warranty does not cover.
Use only recommended transmission fluid
that meets our specifications. See
Automatic Transmission Fluid
Capacity and Specification (page 302).
Note:Use of a non-approved automatic
transmission fluid could cause internal
transmission component damage.
If necessary, add fluid in 8 fl oz (250 ml)
increments through the filler tube until the
level is correct.
If an overfill occurs, remove excess fluid
and have your vehicle checked as soon as
possible.
BRAKE FLUID CHECK
WARNING: Do not use any fluid
other than the recommended brake fluid
as this will reduce brake efficiency. Use
of incorrect fluid could result in the loss
of vehicle control, serious personal injury
or death.
WARNING: Only use brake fluid
from a sealed container. Contamination
with dirt, water, petroleum products or
other materials may result in brake
system damage or failure. Failure to
adhere to this warning could result in the
loss of vehicle control, serious personal
injury or death.
WARNING: Do not allow the fluid
to touch your skin or eyes. If this
happens, rinse the affected areas
immediately with plenty of water and
contact your physician.
WARNING: The brake system
could be affected if the brake fluid level
is below the MIN mark or above the MAX
mark on the brake fluid reservoir.
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Maintenance