
Note:Never use the differential lock at vehicle speeds above 25 mph
(40 km/h).
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
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).
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.
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.
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.
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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WARNING: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.
Note:Do not exceed the GVWR or the GAWR specified on the
certification label.
WARNING:Towing trailers beyond the maximum recommended
gross trailer weight exceeds the limit of the vehicle and could
result in engine damage, transmission damage, structural damage, loss
of vehicle control, vehicle rollover and personal injury.
Model Maximum
GVWR - lb.
(kg)Maximum
GCWR - lb.
(kg)*
F-650 Regular/Super/Crew Cab 26000 (11793) 40000 (18143)
F-750 Regular/Super/Crew Cab 30000 (13608) 45000 (20412)
F-750 Regular/Super/Crew Cab 33000 (14969) 60000 (27216)
* Figures shown are the maximum available for each model. Actual
ratings may be less, depending on your transmission. Check with your
sales consultant for the exact rating on your vehicle.
Preparing to tow
Use the proper equipment for towing a trailer and make sure it is
properly attached to your vehicle. See your dealer or a reliable trailer
dealer if you require assistance.
Hitches
Do not use hitches that clamp onto the vehicle’s bumper or attach to the
axle. You must distribute the load in your trailer so that 10–15% of the
total weight of the trailer is on the tongue.
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Safety chains
Always connect the trailer’s safety chains to the frame or hook retainers
of the vehicle hitch. To connect the trailer’s safety chains, cross the
chains under the trailer tongue and allow slack for turning corners.
If you use a rental trailer, follow the instructions that the rental agency
gives to you.
Do not attach safety chains to the bumper.
Trailer brakes
Electric brakes and manual, automatic or surge-type trailer brakes are
safe if installed properly and adjusted to the manufacturer’s
specifications. The trailer brakes must meet local and Federal
regulations.
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:
•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.
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Servicing after towing
If you tow a trailer for long distances, your vehicle will require more
frequent service intervals. Refer to yourScheduled 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.
•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 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.
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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.
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 toTractor-trailer connectionin theAir suspension
section of 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 toBrakesin this chapter for proper operation of the parking brake
and trailer brakes.
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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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Passenger compartment fuse panel
Fuse/Relay
LocationFuse Amp
RatingFuse Description
1 20A Horn relay
2 15A Flasher
3 20A Cigar lighter
4 10A Diagnostics, Parking brake warning
5 15A Blend door actuator, Climate mode, Back-up
lamps, DRL signal, Heated seats, Trailer ABS,
Exhaust brakes
6 — Not used
7 — Not used
8 5A Radio, GEM 4
9 5A Power window switch LED and relay
10 15A Heated mirrors
11 5A Wiper motor, Washer pump relays
12 10A Stoplamp switch (Hydraulic brake vehicles
only), Allison push-button shifter
13 20A Cluster, Radio
14 10A Interior lamp relay
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4. Remove the jumper cable from the positive (+) terminal of the
disabled vehicle’s battery.
After the disabled vehicle has been started and the jumper cables
removed, allow it to idle for several minutes so the engine computer can
relearnits idle conditions.
WRECKER TOWING INSTRUCTIONS
Before moving the disabled vehicle, check for adequate road clearance of
vehicle components. It is recommended the disabled vehicle be unloaded
prior to being towed to reduce any abnormal load to the vehicle
components resulting from the towing procedures. Before towing, be
sure to fully release the parking brake. The spring-actuated type parking
brake can be reset by recharging the air system with at least 64 psi
(441 kPa) of air. If the brake system will not retain air pressure, then the
spring brakes must be released manually. Refer toParking brakein the
Drivingchapter
Note:For towing, make sure the vehicle is securely connected to the
tow vehicle and the tow vehicle parking brakes are applied before
releasing the disabled vehicle’s spring brakes.
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.
+–+–
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