
To shift the axle from LOW to HIGH with the vehicle moving, accelerate
to approximately 35 mph (56 km/h), press the lower part of the switch
while the transmission is in N (Neutral), then release and apply the
accelerator.
To shift the axle from HIGH to LOW with the vehicle stopped, place the
transmission in N (Neutral), then press the upper part of the switch.
Note:Do not shift the axle to LOW with the vehicle in motion.
Split-shifting (combined axle and transmission shift - manual
transmissions only)
Split-shift sequence
Ratio combination1234567891011
Transmission gear 1st 1st 2nd 2nd 3rd 3rd 4th 4th 5th 6th 6th
Axle range LO HI LO HI LO HI LO HI LO LO HI
To downshiftthe axle to a slower ratio and shift the transmission, shift
the transmission and move the switch to the lower ratio before the
clutch is re-engaged.
To upshiftthe axle and shift the transmission, move the switch to a
faster ratio and make the transmission shift in the usual manner.
Ratio extender use
Low end:A two-speed axle can be used as a ratio-extender when
split-shifting is not necessary. For low end use, just shift the axle into
LOW to start out, and shift to HIGH when the extra torque is no longer
needed.
Transmission (5-speed) 1st 1st 2nd 3rd 4th 5th 6th
Two-speed axle Axle low Axle high
High end:To use the two-speed axle as a high end ratio-extender, stay
in the LOW range for normal upshifts and only shift the axle to HIGH on
the freeway for greater road speed.
Transmission (5-speed) 1st 2nd 3rd 4th 5th 6th
Two-speed axle Low for gradeability Axle high
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•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 requires 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 clears 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 are 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 specificationsin 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 withoutaP[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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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 does not retain air pressure, then the spring brakes must
be released manually. Refer toParking brakein theDrivingchapter.
Note:For towing, make sure the vehicle is securely connected to the
tow vehicle and the tow vehicle’s 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:
•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.
+–+–
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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 prevents 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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Tightening steering column joint bolts
As a good maintenance practice, it is recommended that steering column
joint bolts be checked for tightness every 60,000 miles (96,000 km) or
annually, whichever occurs first. DO NOT OVERTIGHTEN.
Power steering hydraulic system
Whenever the power steering’s hydraulic system has been drained and
refilled for any reason, air must be bled from the system before returning
the vehicle to service. Failure to properly bleed the hydraulic system can
result in degradation of power system performance.
Consult your dealer who is aware of the proper procedures for filling and
bleeding the system.
OPENING THE HOOD
The hood and fenders are held in position by a latch located on each
fender.
WARNING:The parking brake must be fully set before opening
the hood or possible personal injury may occur.
WARNING:To reduce the risk of the possibility of personal
injury, never stand beneath the hood when it is being raised or
lowered.
WARNING:If you must leave the engine running while checking
under the hood, do not allow any loose clothing, jewelry, hair or
other items to get near moving engine components or possible personal
injury may occur.
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.
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The engine speed may increase slightly. To allow parked regeneration to
continue uninterrupted:
1. The vehicle must remain parked
2. The transmission must remain in P (Park) or N (Neutral) (as
previously described in Step 2).
3. The accelerator pedal, service brake pedal, and clutch pedal (if
equipped) must not be pressed
4. The parking brake must remain set
On average (depending on filter level and other factors), the process takes
20–30 minutes to complete. The DPF lamp turns off when the process is
complete. Repeat Steps 1–5, if parked regeneration is interrupted.
To discontinue parked regeneration
Press any of the floor pedals to discontinue parked regeneration.
Diesel particulate filter maintenance and service
The DPF is designed to retain a relatively large amount of residual ash
and provide many miles and hours of maintenance-free operation. At
some point, generally beyond 150,000 miles (240,000 km) or 5,000 hours
of operation (whichever comes first), the DPF requires professional
cleaning to remove the accumulated ash.
The exact number of miles or hours of operation varies greatly depending
upon vehicle/engine loading and operating conditions, ash content of the
engine oil, and quality of the diesel fuel used in your truck. Adhering to
your engine manufacturer’s recommended oil and fuel specifications
maximizes the miles and hours of operation before a DPF professional
cleaning is required. Refer to your engine manufacturer’s owner’s manual for
more details regarding recommended maintenance and service of your DPF.
Exhaust outlet assembly
WARNING:The normal operating temperature of the exhaust
system is very high. Never work around or attempt to repair any
part of the exhaust system until it has cooled. Failure to follow these
instructions may result in serious personal injury.
The exhaust outlet assembly on your vehicle is a uniquely functioning
device that accompanies the DPF assembly. It is designed to help control
the temperature of the exhaust during the DPF regeneration process.Do
not modify or remove this device. Modification of the system
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Exhaust System:
•Inspect for leaks at various joint connections and loose clamps.
•Perform a visual inspection for cracks or holes in the muffler and tail
pipe.
•Always use the recommended parts when items need to be replaced.
•Do not change the tail pipe elbow or offset tail pipe orientation from
the standard position as originally received.
•To avoid abnormal changes in vehicle sound levels, it is necessary for
the owner to perform inspections and necessary maintenance at the
intervals shown in theScheduled Maintenance Guidechapter.
POWER STEERING FLUID
Check the power steering fluid level using the following procedure:
1. Set the parking brake, shift into N (Neutral) (automatic transmission)
or 1 (First) (manual transmission) and turn the engine off.
2. Open the hood.
3. Clean the top of the power steering fluid reservoir.
4. Remove the dipstick from the reservoir and wipe the dipstick clean.
5. Reinstall the dipstick. Remove it again and check the fluid level.
•Check the COLD side of the
dipstick if the fluid is cool or
warm to the touch
(approximately 68°-120°F
[20°-49°C]); the fluid level should
be within the FULL range. If
necessary, add fluid in small
amounts, continuously checking
the level, until it reaches the proper level.
•Check the HOT side of the
dipstick if the fluid is too hot to
touch (approximately 176°–230°F
[80°-110°C]); the fluid level
should be within the FULL range.
If necessary, add fluid in small
amounts, continuously checking
the level, until it reaches the
proper level.
Whenever the dipstick is installed, make sure it is properly seated and
tightened securely.
ADD MAX. COLDFULL
ADD MAX. HOTFULL
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Transmission and clutch
removed for clarity
3. Lubricate the clutch release bearing (at one location) and the clutch
release shaft (at two locations), using the grease fittings provided, with a
grease gun.
4. Lubricate clutch release wear pads at the two locations where they
contact the clutch release bearing with a brush or similar tool.
5. Install the inspection cover onto the clutch housing.
Refer to theScheduled Maintenance Guidechapter for the service
interval schedules.
TRANSMISSION FLUID
Automatic transmission fluid
Refer to yourAllison Automatic Transmission Operator’s Manualfor
scheduled transmission fluid check/change intervals. Your transmission
does not consume fluid. However, the fluid level should be checked if the
transmission is not working properly, i.e., if the transmission slips or
shifts slowly or if you notice some sign of fluid leakage.
Automatic transmission fluid expands when warmed. To obtain an
accurate fluid check, drive the vehicle until it is warmed up
(approximately 20 miles [30 km]). If your vehicle has been operated for
an extended period at high speeds, in city traffic or during hot weather,
the vehicle should be turned off for about 30 minutes to allow fluid to
cool before checking.
1. Drive the vehicle 20 miles (30 km) or until it reaches normal operating
temperature.
2. Park the vehicle on a level surface and engage the parking brake.
3. With the parking brake engaged and your foot on the brake pedal,
start the engine and move the gearshift lever through all of the gear
ranges. Allow sufficient time for each gear to engage.
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