PTO operation while vehicle is moving
After the PTO is engaged for driven vehicle operation, shift to the
desired range and drive the vehicle. The speed of the PTO, during this
period of operation, will always maintain direct relation to vehicle speed.
PTO speed will decrease in relation to vehicle (transmission output)
speed as shifts to a higher gear occur. When operating the PTO while the
vehicle is moving, the PTO may be disengaged whenever it is no longer
required. When there is no load on the PTO gear, it can be pulled out of
engagement.
Vehicles equipped with an Allison 3000 Series automatic
transmission
The PTO drive gear is engine-driven and provides direct engine power.
The PTO can be operated when the vehicle is either stationary or
moving.
The PTO gear is in constant mesh with the drive gear in the torque
converter housing. A friction clutch or constant drive is used to transmit
power to the PTO.
Vehicles equipped with an Eaton UltraShift transmission
Refer to the operationTransmission Power Take Offsection of the
UltraShift Driver Instructions Manual.
Vehicles equipped with a manual transmission
Transmission-mounted PTO units are available for local installation on
your vehicle. See yourBody Builder’s Layout Bookfor restrictions on
use and installation of PTO units.
To engage the PTO unit, stop the vehicle and place the transmission in N
(Neutral). Press the clutch and allow the gears to stop rotating, then
engage the PTO unit. The PTO can also be selected with the
transmission in gear as long as the clutch is pressed.
When operating the PTO with the vehicle stationary, first set the parking
brake (chock the wheels if the vehicle is on a hill or another uneven
surface).
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REAR AXLE INFORMATION
Axle operating temperature normally will not exceed 100°F (38°C). If
the operating temperature exceeds 230°F (110°C), the rate of axle
lubrication oxidation will increase and shorten the life of the lubricant
and seals, requiring axle lubrication changes to become more frequent to
preserve the axle. Extreme Pressure (EP) lubricants should not be run
consistently above 230°F (110°C).
Gross axle weight
Your truck has gross axle weight, gross vehicle weight and gross
combination weight ratings. Do not exceed these ratings.
WARNING:Exceeding these ratings by overloading can cause
component failure resulting in property damage, personal injury
or death.
Rear axles with locking or limited-slip differentials (if equipped)
If your vehicle is equipped with a locking or limited-slip differential, note
the following:
•Power will be transmitted to the opposite wheel should one of the
wheels begin to slip.
•Both wheels must be raised off the ground should it be necessary to
operate one wheel with the vehicle stationary.
WARNING:If both wheels are not raised off the ground, the
one wheel that is not raised may pull the vehicle off its support,
possibly resulting in personal injury
Driver-controlled differential lock
To prevent the vehicle from moving when servicing the wheels, tires or
brakes, turn the engine off and raise all drive wheels of the locker
differential axle. Axles equipped with NoSPIN Detroit Locker differentials
deliver power to both wheels even when only one wheel is on the
ground.
WARNING: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.
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Care should be taken to avoid sudden accelerations when both drive
wheels are on a slippery surface.
WARNING: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 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).
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.
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WARNING:Do not use replacement tires with lower load
carrying capacities than the originals because they may lower
the vehicle’s GVWR and GAWR limitations. Replacement tires with a
higher limit than the originals do not increase the GVWR and GAWR
limitations.
WARNING:Exceeding any vehicle weight rating limitation could
result in serious damage to the vehicle and/or personal injury.
Unloaded or lightly loaded vehicles
The braking system has been designed to safely stop your vehicle when
fully loaded to its GVWR.
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.
Consult your local motor vehicle speed regulations for towing a trailer.
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.
Note:Do not exceed the GCWR rating or transmission damage may
occur.
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.
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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.
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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.
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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 toTractor-trailer connectionsin 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.
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.
Press 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.
Passenger compartment fuse panel
The fuse box is located behind the passenger airbag cover and can be
accessed through the glove box.
Roadside Emergencies
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