
3. The transfer casewill notshift.
NOTE: Before retrying a selection, make certain that all
the necessary requirements for selecting a new transfer
case position have been met. To retry the selection, turn the
control switch back to the current position, wait five
seconds, and retry selection. To find the shift requirements,
refer to the Shifting Procedure for your transfer case,
located in this section.
The “SVC 4WD Warning Light” monitors the electronic
shift four-wheel drive system. If this light remains on after
engine start up or illuminates during driving, it means that
the four-wheel drive system is not functioning properly
and that service is required.
WARNING!
Always engage the parking brake when powering
down the vehicle if the “SVC 4WD Warning Light” is
illuminated. Not engaging the parking brake may
allow the vehicle to roll, which may cause personal
injury. NOTE:
Do not attempt to make a shift while only the front
or rear wheels are spinning, as this can cause damage to
driveline components.
When operating your vehicle in 4WD LOW, the engine
speed is approximately three times that of the 2WD or
4WD LOCK positions at a given road speed. Take care not
to overspeed the engine and do not exceed 25 mph
(40 km/h).
Proper operation of four-wheel drive vehicles depends on
tires of equal size, type and circumference on each wheel.
Any difference in tire size can cause damage to the
drivetrain.
Because four-wheel drive provides improved traction,
there is a tendency to exceed safe turning and stopping
speeds. Do not go faster than road conditions permit.
6
STARTING AND OPERATING 263

Payload
The payload of a vehicle is defined as the allowable load
weight a truck can carry, including the weight of the driver,
all passengers, options and cargo.
Gross Axle Weight Rating (GAWR)
The GAWR is the maximum permissible load on the front
and rear axles. The load must be distributed in the cargo
area so that the GAWR of each axle is not exceeded.
Each axle GAWR is determined by the components in the
system with the lowest load carrying capacity (axle,
springs, tires or wheels). Heavier axles or suspension
components sometimes specified by purchasers for in-
creased durability does not necessarily increase the vehi-
cle’s GVWR.
Tire Size
The tire size on the Vehicle Certification Label represents
the actual tire size on your vehicle. Replacement tires must
be equal to the load capacity of this tire size.
Rim Size
This is the rim size that is appropriate for the tire size
listed.
Inflation Pressure
This is the cold tire inflation pressure for your vehicle for
all loading conditions up to full GAWR.
Curb Weight
The curb weight of a vehicle is defined as the total weight
of the vehicle with all fluids, including vehicle fuel, at full
capacity conditions, and with no occupants or cargo loaded
into the vehicle. The front and rear curb weight values are
determined by weighing your vehicle on a commercial
scale before any occupants or cargo are added.
Loading
The actual total weight and the weight of the front and rear
of your vehicle at the ground can best be determined by
weighing it when it is loaded and ready for operation.
The entire vehicle should first be weighed on a commercial
scale to insure that the GVWR has not been exceeded. The
weight on the front and rear of the vehicle should then be
determined separately to be sure that the load is properly
distributed over the front and rear axle. Weighing the
vehicle may show that the GAWR of either the front or rear
axles has been exceeded but the total load is within the
specified GVWR. If so, weight must be shifted from front to
rear or rear to front as appropriate until the specified
6
STARTING AND OPERATING 291

WARNING!(Continued)
cause a loss of control, poor performance or damage
to brakes, axle, engine, transmission, steering, sus-
pension, chassis structure or tires.
•
Safety chains must always be used between your ve-
hicle and trailer. Always connect the chains to the hook
retainers of the vehicle hitch. Cross the chains under the
trailer tongue and allow enough slack for turning cor-
ners.
• Vehicles with trailers should not be parked on a
grade. When parking, apply the parking brake on the
tow vehicle. Put the tow vehicle transmission in
PARK. For four-wheel drive vehicles, make sure the
transfer case is not in NEUTRAL. Always, block or
chock the trailer wheels.
• GCWR must not be exceeded.
• Total weight must be distributed between the tow
vehicle and the trailer such that the following four
ratings are not exceeded:
1. GVWR
2. GTW
3. GAWR
4. Tongue weight rating for the trailer hitch utilized.
Towing Requirements — Tires
• Do not attempt to tow a trailer while using a compact
spare tire.
• Proper tire inflation pressures are essential to the safe
and satisfactory operation of your vehicle. Refer to
“Tires” in “Servicing And Maintenance” for proper tire
inflation procedures.
• Check the trailer tires for proper tire inflation pressures
before trailer usage.
• Check for signs of tire wear or visible tire damage before
towing a trailer. Refer to “Tires” in “Servicing And
Maintenance” for the proper inspection procedure.
• When replacing tires, refer to “Tires” in “Servicing And
Maintenance” for the proper tire replacement proce-
dures. Replacing tires with a higher load carrying capac-
ity will not increase the vehicle’s GVWR and GAWR
limits.
Towing Requirements — Trailer Brakes
• Do not interconnect the hydraulic brake system or
vacuum system of your vehicle with that of the trailer.
This could cause inadequate braking and possible per-
sonal injury.
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STARTING AND OPERATING 301

towing conditions change. Changes to towing conditions
include trailer load, vehicle load, road conditions and
weather.
Adjusting GAIN
NOTE:This should only be performed in a traffic free
environment at speeds of approximately 20–25 mph
(30–40 km/h).
1. Make sure the trailer brakes are in good working condition, functioning normally and properly adjusted.
See your trailer dealer if necessary.
2. Hook up the trailer and make the electrical connections according to the trailer manufacturer’s instructions.
3. When a trailer with electric/EOH brakes is plugged in, the trailer connected message should appear in the
instrument cluster display (if the connection is not
recognized by the ITBM, braking functions will not be
available), the GAIN setting will illuminate and the
correct type of trailer must be selected from the instru-
ment cluster display options. 4. Push the UP or DOWN button on the steering wheel
until “TRAILER TOW” appears on the screen.
5. Push the RIGHT arrow on the steering wheel to enter “TRAILER TOW”.
6. Push the UP or DOWN buttons until the Trailer Brake Type appears on the screen.
7. Push the RIGHT arrow and then push the UP or DOWN buttons until the proper Trailer Brake Type appears on
the screen.
8. In a traffic-free environment, tow the trailer on a dry, level surface at a speed of 20–25 mph (30–40 km/h) and
squeeze the manual brake control lever completely.
9. If the trailer wheels lockup (indicated by squealing tires), reduce the GAIN setting; if the trailer wheels turn
freely, increase the GAIN setting.
Repeat steps 8 and 9 until the GAIN setting is at a point just
below trailer wheel lockup. If towing a heavier trailer,
trailer wheel lockup may not be attainable even with the
maximum GAIN setting of 10.
304 STARTING AND OPERATING

JACKING AND TIRE CHANGING
WARNING!
•Do not attempt to change a tire on the side of the
vehicle close to moving traffic. Pull far enough off
the road to avoid the danger of being hit when
operating the jack or changing the wheel.
• Being under a jacked-up vehicle is dangerous. The
vehicle could slip off the jack and fall on you. You
could be crushed. Never put any part of your body
under a vehicle that is on a jack. If you need to get
under a raised vehicle, take it to a service center
where it can be raised on a lift.
• Never start or run the engine while the vehicle is on
a jack.
• The jack is designed to be used as a tool for changing
tires only. The jack should not be used to lift the
vehicle for service purposes. The vehicle should be
jacked on a firm level surface only. Avoid ice or
slippery areas.
4500/5500 Models
These vehicles do not come equipped with a jack.
NOTE: Jacking and tire changing on 4500/5500 models
should be performed by an authorized dealer, or knowl-
edgeable service personnel with the appropriate heavy
duty equipment, like a tire service company.
Preparations For Jacking
1. Park the vehicle on a firm, level surface. Avoid ice or slippery areas.
WARNING!
Do not attempt to change a tire on the side of the
vehicle close to moving traffic, pull far enough off the
road to avoid being hit when operating the jack or
changing the wheel.
2. Place the gear selector into PARK. On four-wheel drive vehicles, shift the transfer case to the 4L position.
3. Turn on the Hazard Warning flasher.
4. Apply the parking brake.
5. Turn the ignition OFF.
7
IN CASE OF EMERGENCY 339

6. Block both the front and rear of the wheel diagonallyopposite the jacking position. For example, if the right
front wheel is being changed, block the left rear wheel.
NOTE:Passengers should not remain in the
vehicle when the vehicle is being jacked.
Jacking Instructions 4500 And 5500 Series
WARNING!
Carefully follow these tire changing warnings to help
prevent personal injury or damage to your vehicle:
•
Always park on a firm, level surface as far from the edge
of the roadway as possible before raising the vehicle.
• Turn on the Hazard Warning flasher.
• Block the wheel diagonally opposite the wheel to be
raised.
• Set the parking brake firmly and set the transmission
in PARK.
• Never start or run the engine with the vehicle on a
jack.
(Continued)
WARNING! (Continued)
•Do not let anyone sit in the vehicle when it is on a
jack.
• Do not get under the vehicle when it is on a jack. If
you need to get under a raised vehicle, take it to a
service center where it can be raised on a lift.
• Only use the jack in the positions indicated and for
lifting this vehicle during a tire change.
• If working on or near a roadway, be extremely
careful of motor traffic.
• To assure that spare tires, flat or inflated, are securely
stowed, spares must be stowed with the valve stem
facing the ground.
340 IN CASE OF EMERGENCY

When changing a rear wheel, assemble the jack driver to
the jack and connect the jack driver to the extension tubes.
Securely place the jack under the sway bar bracket (unless
both tires are flat on one side, then place jack under shock
bracket) facing forward in vehicle. Connect the extension
tubes and lug wrench.Before raising the wheel off the ground, make sure that
the jack will not damage surrounding truck parts and
adjust the jack position as required.
NOTE:
If the jack will not lower by turning the dial
(thumbwheel) by hand, it may be necessary to use the jack
driver in order to lower the jack.
4. By rotating the lug wrench clockwise, raise the vehicle until the wheel just clears the surface.
WARNING!
Raising the vehicle higher than necessary can make the
vehicle less stable. It could slip off the jack and hurt
someone near it. Raise the vehicle only enough to
remove the tire.
5. Remove the lug nuts and pull the wheel off. Install the spare wheel and lug nuts with the cone shaped end of
the nuts toward the wheel on single rear wheel (SRW)
models. On dual rear wheel models (DRW) the lug nuts
are a two-piece assembly with a flat face. Lightly tighten
the nuts. To avoid risk of forcing the vehicle off the jack,
do not fully tighten the nuts until the vehicle has been
lowered.
Rear Jacking Location
342 IN CASE OF EMERGENCY

6. Using the lug wrench, finish tightening the nuts using acrisscross pattern. For the proper lug nut torque speci-
fications refer to “Wheel And Tire Torque Specifica-
tions” in “Technical Specifications.” If in doubt about
the correct tightness, have them checked with a torque
wrench by an authorized dealer or at a service station.
WARNING!
A loose tire or jack thrown forward in a collision or
hard stop, could endanger the occupants of the vehicle.
Always stow the jack parts and the spare tire in the
places provided.
7. Install wheel center cap (if equipped) and remove wheel blocks. Do not install chrome or aluminum wheel center
caps on the spare wheel. This may result in cap damage.
8. Lower the jack to its fully closed position. If the jack will not lower by turning the dial (thumbwheel) by hand, it
may be necessary to use the jack driver in order to lower
the jack. Stow the replaced tire, jack, and tools as
previously described.
9. Adjust the tire pressure when possible.
Dual Rear Wheels
Slots in the wheels will assist in properly orienting the
inner and outer wheels. Align these slots when assembling
the wheels for best access to the tire valve on the inner
wheel. The tires of both dual wheels must be completely off
the ground when tightening to insure wheel centering and
maximum wheel clamping.
Dual wheel models require a special heavy-duty lug nut
tightening adapter (included with the vehicle) to correctly
tighten the lug nuts. Also, when it is necessary to remove
and install dual rear wheels, use a proper vehicle lifting
device.
NOTE: When installing a spare tire (if equipped) as part of
a dual rear wheel end combination, the tire diameter of the
two individual tires must be compared. If there is a
significant difference, the larger tire should be installed in
a front location. The correct direction of rotation for dual
tire installations must also be observed.
It is recommended that wheel stud nuts be kept torqued to
specifications at all times. Torque wheel stud nuts to
specifications at each lubrication interval.
7
IN CASE OF EMERGENCY 343