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WARNING: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:
•Do not drive faster than 70 mph (113 km/h) during the first 500 miles
(800 km) of trailer towing 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.
•Use a lower gear to eliminate excessive shifting and assist in
transmission cooling.
•Allow more distance for stopping with a trailer attached; anticipate
stops and brake gradually.
Servicing after towing
If you tow a trailer for long distances, your vehicle will require more
frequent service intervals. Refer to theScheduled Maintenance Guide
chapter 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.
•The trailer tongue weight should be 10–15% of the loaded trailer
weight.
Driving
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•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 toLubricant specificationsin theMaintenance and
Specificationschapter 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 without a P [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
WARNING: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.
WARNING: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.
Driving
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Fuse/Relay
locationFuse amp
ratingFuse description
1 20A Horn
2 15A Flasher relay
3 20A Power point
4 10A Data Link Connector (DLC), Engine
diagnostic connector, Parking brake warning
5 15A Run relay
6 — Not used
7 — Not used
8 5A Radio, GEM
9 5A Power window relay
10 15A Heated mirrors
11 5A Wiper and washer systems
12 10A Transmission shift selector
13 20A Radio, Power mirrors
14 10A Interior lamp relay
15 10A Interior lamp relay
16 15A High beams, Indicator
17 — Not used
18 5A Dimmer switch, Interior lighting
19 15A Engine control
20 5A Starting system
21 10A DRL resistor
22 15A Air horn, Air suspension dump, Two-speed
axle, Driver-controlled locking differential
23 10A Flasher relay
24 15A ABS relay, Fuel heater relay, Air dryer
25 10A Blower motor relay
26 10A Right-hand low beam headlight
27 — Not used
28 10A Left-hand low beam headlight
29 10A Cluster, GEM
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Fuse/Relay
locationFuse amp
ratingFuse description
30 15A Allison electronic transmission
31 15A Mirror fold relay
Relay 1 — Interior lamps
Relay 2 — Not used
Relay 3 — Horn
Relay 4 — Not used
Relay 5 — Not used
Power distribution box
WARNING:Always disconnect the battery before servicing high
current fuses.
WARNING:To reduce risk of electrical shock, always replace
the cover to the Power Distribution Box before reconnecting the
battery or refilling fluid reservoirs.
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Fuse/Relay
LocationFuse Amp
RatingDescription
R2 — Trailer tow marker lamp relay
R3 — Trailer tow stop lamp relay
R4 — Trailer tow tail lamp relay
R5 — Not used
R6 — Not used
R7 — Trailer tow left turn lamp relay
R8 — Trailer tow right turn lamp relay
*Maxi fuse
Inline fuses
Your vehicle may have several inline fuses located in/on the battery
cables located in the battery box depending on application.
•All Allison transmission equipped vehicles have a 10 Amp fuse located
in the clean power cables located in the battery box.
•All vehicles have a 30 Amp fused located in the clean power cables
located in the battery box.
•All vehicles equipped with an Eaton transmission have a 30 Amp fuse
located in the clean power cables located in the battery box.
•All Hydraulic brake equipped vehicles have a 40 Amp fuse located in
the clean power cables located in the battery box and in addition
another 30 Amp fuse located in a fuse holder just above the power
distribution center located in the vehicles engine compartment.
JUMP STARTING
WARNING:The gases around the battery can explode if
exposed to flames, sparks, or lit cigarettes. An explosion could
result in injury or vehicle damage.
WARNING:Batteries contain sulfuric acid which can burn skin,
eyes and clothing, if contacted.
Do not attempt to push-start your automatic transmission
vehicle. Automatic transmissions do not have push-start
capability. Attempting to push-start a vehicle with an automatic
transmission may cause transmission damage.
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WARNING: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 driveshaft is required.
Note:To avoid transmission damage, vehicles should not be towed even
a short distance without suspending rear wheels or removing the axle
shafts or driveshaft.
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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Installing the axle shafts
1. Remove the covers from the wheel ends.
2. Shift the differential lock to the unlocked (disengaged) position.
3. Install the axle shafts.
•Place the gaskets on the wheel hub studs.
•Push the right-hand axle shaft and gasket into the wheel end and
housing until the shaft stops against the differential shift collar.
•Push down and in on the axle shaft flange and rotate the shaft until
the splines of the shaft and shift collar are engaged.
•Push the axle shaft further into the housing until the shaft stops
against the differential side gear.
•Push down on the axle shaft flange and rotate the shaft until the
splines of the shaft and side gear are engaged.
•Push the axle shaft completely into the housing until the axle shaft
flange and the gasket are flush against the wheel hub.
•Install the left-hand axle shaft and gasket into the wheel end.
4. If tapered dowels are required, install them at each stud and into the
flange of the axle shaft. Use a punch or drift and hammer, if needed.
5. Install the fasteners and tighten to correct torque value. Refer to the
Service Manual.
Towing the vehicle with the rear wheels suspended
Note:To avoid damage to the cab roof or air deflector when towing the
vehicle backward (rear wheels suspended) the air deflector must be
removed.
Whenever possible, it is preferable to tow a disabled vehicle from the
rear by raising the rear of the chassis. When towing a vehicle with the
rear of the chassis suspended, the front wheels must be locked in the
straight-ahead position.
Vehicles equipped with a manual transmission must have at least 1.0 pint
(0.5L) of transmission fluid drained from the case. This will prevent the
transmission fluid from entering the clutch housing and fluid saturating
the clutch discs. Make sure that the transmission fluid is replaced before
the vehicle is returned to service.
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To open the hood:
1. Set the parking brake, shift into N (Neutral) (automatic transmission)
or 1 (First) (manual transmission) and turn the engine off.
2. Lift upward on the bottom of
each latch.
3. Pull the bottom of each latch
away from the fender.
4. Tilt the hood forward until
stopped by the retaining cables.
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