
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.
Care should be taken to avoid sudden accelerations when both drive
wheels are on a slippery surface.
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.
Some Dana/Spicer drive axles have a driver-controlled differential lock.
The differential lock can lock or unlock the differential when the vehicle
is moving or stopped. When extra traction is required, the differential
lock will provide full power to both axles.
When the differential is locked, the vehicle’s turning radius will increase
(vehicle will “under-steer”)
The differential can be locked or unlocked when the vehicle is moving at
a constant speed of less than 25 mph (40 km/h) and while the wheels
are not slipping. The differential must not be locked when the vehicle is
traveling down steep grades and traction is minimal.
Note: Never use the differential lock at vehicle speeds above 25 mph (40
km/h).
Note: The driver-controlled differential lock function will vary with some
transmissions.
• Vehicles equipped with an Allison 3000 Series transmission: The
differential lock and differential lock light will automatically disengage
at speeds above 25 mph (40 km/h). The differential lock will remain
off until either the vehicle is restarted or the differential lock switch is
turned off then back on.
• Vehicles equipped with a 5–speed, 6–speed or 7–speed manual:
The differential lock and differential lock light will automatically
disengage at speeds above 25 mph (40 km/h). The differential lock
will remain off until either the vehicle is restarted or the differential
lock switch is turned off then back on.
Axle conversions
It is not recommended, or approved, for axle conversions to be
performed. However, it is understood that, on occasion, aftermarket
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add-on axles are installed by others on the truck chassis which allow
operator control for weight transfer from other axles (i.e., air lift axles).
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.
TWO-SPEED REAR AXLE (IF EQUIPPED)
A two-speed rear axle allows the driver to select a LO range for greater
pulling power and a HI range for greater road speed and fuel economy.
These ranges can also be used to provide additional steps between
transmission shifts when driving on steep grades and/or fuel economy
may be factors.
Note: Do not shift between ranges when the speed control is on.
Never shift a two-speed axle when descending a steep grade as
this may cause loss of vehicle control and result in personal injury.
Axle shifting
Manual transmissions:
•To downshift, select the next lower gear, release and depress the
accelerator pedal rapidly, or while holding the accelerator pedal down,
release and engage the clutch rapidly. Note:The clutch method is
recommended when driving at slower speeds.
• To upshift, keep the accelerator pedal down, select the next higher
gear, release the accelerator and pause until the axle upshifts. Note:
De-clutch for smoother axle upshifts when driving at slower speeds.
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•Canada
Under no circumstances should your vehicle be loaded in excess of the
GVWR or GAWR. It is the operator’s responsibility to ensure that neither
the axle capacities, spring capacities, tire capacities nor the vehicle rated
GVWR is exceeded. For tire capacities, refer to Maintenance and
Specifications chapter.
Unloaded or lightly loaded vehicles
The braking system has been designed to safely stop your vehicle when
fully loaded to its GVWR.
When operating empty or lightly loaded, sudden or hard braking
may induce wheel lockup with loss of vehicle control and the
possibility of accident and serious injury, especially on wet or slippery
road surfaces.
TRAILER TOWING
Towing a trailer places an additional load on your vehicle’s engine,
transmission, axle, brakes, tires and suspension. Inspect these
components carefully prior to and after any towing operation.
Your vehicle’s load capacity is designated by weight, not by volume, so
you cannot necessarily use all available space when loading a vehicle.
2nd unit bodies are not included in maximum trailer weight ratings. The
weight of the additional “body” must be subtracted from the maximum
trailer weight.
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Do not connect a trailer’s hydraulic brake system directly to your
vehicle’s brake system. Your vehicle may not have enough
braking power and your chances of having a collision greatly increase.
Trailer lamps
Trailer lamps are required on most towed vehicles. Your vehicle may be
equipped with one of two possible trailer wiring designs. Make sure all
running lights, brake lights, turn signals and hazard lights are working.
See your dealer or trailer rental agency for proper instructions and
equipment for hooking up trailer lamps.
Driving while you tow
When towing a trailer:
• Keep your speed no faster than 70 mph (112 km/h) during the first
500 miles (800 km) of towing a trailer, and don’t make full throttle
starts.
• Turn off the speed control. The speed control may shut off
automatically when you are towing on long, steep grades.
• Consult your local motor vehicle speed regulations for towing a trailer.
• To eliminate excessive transmission shifting, use a lower gear. This will
also assist in transmission cooling.
• Anticipate stops and brake gradually.
• Do not exceed the GCWR rating or transmission damage may occur.
Servicing after towing
If you tow a trailer for long distances, your vehicle will require more
frequent service intervals. Refer to your Scheduled Maintenance Guide
for more information.
Trailer towing tips
• Practice turning, stopping and backing up before starting on a trip to
get the feel of the vehicle trailer combination. When turning, make
wider turns so the trailer wheels will clear curbs and other obstacles.
• Allow more distance for stopping with a trailer attached.
• If you are driving down a long or steep hill, shift to a lower gear. Do
not apply the brakes continuously, as they may overheat and become
less effective.
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•The trailer tongue weight should be 10–15% of the loaded trailer
weight.
• If you will be towing a trailer frequently in hot weather, hilly
conditions, at GCW, or any combination of these factors, consider
refilling your rear axle with synthetic gear lube if not already so
equipped. Refer to Lubricant specifications in theMaintenance and
Specifications chapter for the lubricant specification. Remember that
regardless of the rear axle lube used, do not tow a trailer for the first
500 miles (800 km) of a new vehicle, and that the first 500 miles (800
km) of towing be done at no faster than 70 mph (112 km/h) with no
full throttle starts.
• After you have traveled 50 miles (80 km), thoroughly check your
hitch, electrical connections and trailer wheel lug nuts.
• To aid in engine/transmission cooling and A/C efficiency during hot
weather while stopped in traffic, place the gearshift lever in P (Park)
(if available on your automatic transmission) or N (Neutral) (manual
transmissions and automatic transmissions withou taP[Park]
position).
• Vehicles with trailers should not be parked on a grade. If you must
park on a grade, place wheel chocks under the trailer’s wheels.
FIFTH WHEEL OPERATION
Failure to follow the fifth wheel manufacturer’s instructions for
hooking and unhooking as well as sliding the fifth wheel could
result in an accident, personal injury or death.
When the tractor and trailer are parked unattended, the trailer
brake hand control should never be used to apply the brake,
since air may leak from the system, allowing vehicle movement,
resulting in possible property damage, personal injury or death.
Before hook-up, make sure:
• The fifth wheel jaws are fully opened.
• The fifth wheel is fully tilted back to prevent body damage when the
tractor is backed under a trailer.
• The trailer wheels are blocked and the trailer spring brakes are
adjusted and applied. Never chase a trailer.
• The brake hoses and light cords are clear of the fifth wheel.
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Hook-up
1.
Back the tractor squarely under the trailer, engaging the fifth wheel jaws
on the kingpin. Always back-up slowly, making sure the trailer is neither too
high nor too low. Avoid backing under the trailer from an angle.
2. Connect the service and emergency brake hoses and trailer light
connector. Refer to Tractor-trailer connection in this chapter, adhering
to the warning and using the three-point stance while connecting and
disconnecting the trailer.
3.
Inspect the jaws of the fifth wheel to be sure they have fully closed on
the trailer kingpin and the trailer plate is resting securely on the fifth wheel.
4. Be sure the coupler release lever is in the locked position.
5. Charge the trailer brake system. Set the trailer brakes, either with the
hand valve or tractor protection valve. Pull against the trailer for an
additional check of proper hook-up. Do not pull hard enough to damage
or strain the equipment.
6. Set the tractor parking brakes and fully raise the trailer landing gear.
Refer to Brakesin this chapter for proper operation of the parking brake
and trailer brakes.
7. Check the operation of all trailer lights and correct any lights that may
be faulty.
Un-hook
1. Try to keep the tractor and trailer in a straight line.
2. Apply the parking brakes.
3. Lower the trailer landing gear, making sure it is on solid, level ground.
The weight of the trailer is to be on the landing gear.
4. Block the trailer wheels.
5. Disconnect the brake hoses and light cords. Be sure hoses and cords
are clear.
6. Pull coupler release lever to disengage the fifth wheel jaws.
7. Release the tractor parking brakes.
8. Pull out from the trailer slowly, allowing the landing gear to take the
load gradually.
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HAZARD FLASHER
The hazard flasher control is located
on the steering column, just behind
the steering wheel. The hazard
flashers will operate when the
ignition is off.
Push in the flasher control and all
front and rear direction signals will
flash. Press the flasher control again
to turn them off. Use it when your
vehicle is disabled and is creating a
safety hazard for other motorists.
Note:With extended use, the flasher may run down your battery.
FUSING
If electrical components in the vehicle are not working, a fuse may have
blown. Blown fuses are identified by a broken wire within the fuse.
Check the appropriate fuses before replacing any electrical components.
Note:Always replace a fuse with one that has the specified amperage
rating. Using a fuse with a higher amperage rating can cause severe wire
damage and could start a fire.
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To reduce the risk of personal injury or property damage when
manually releasing the spring brakes, be sure to block the wheels
so the vehicle cannot move once the brakes are released.
Towing the vehicle with the front wheels suspended
When it is necessary to tow a vehicle with the front wheels suspended,
extra precautions must be taken to avoid transmission or differential
damage. Proceed as follows:
•Remove the axle shafts from the axle assembly to prevent the wheels
from driving the differential and the transmission.
•The wheel hub ends must be covered to prevent loss of axle lubricant
and entrance of other contaminants. If the axle shafts are not
removed, removal of the propeller shaft is required.
Note:To avoid transmission damage, vehicles should not be towed even
a short distance without suspending rear wheels or removing the axle
shaft or propeller shaft.
Note:In the event the chassis is equipped with a tandem axle and the
vehicle is to be towed from the front, the forward rear axle may be
raised to clear the road surface and secured to the frame by chains or
U-bolts, allowing only the rear rear axle to contact the road surface. Axle
shafts must be removed from the rear rear axle assembly. The wheel hub
ends must be covered to prevent loss of axle lubricant and entrance of
contaminants. Use extreme care in securing the chains or U-bolts to
avoid possible damage to the brake lines, hoses or other components.
Towing vehicles equipped with a driver-controlled differential lock
Note:If the vehicle must be towed to a service facility with the drive
axle wheels on the ground, it is necessary to remove the axle shafts
before the vehicle is towed.
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