more quickly. If you force the gearshift lever into position, this action
defeats the purpose of the synchronizer by causing gear clash.
Shifting with a Non-Synchronized Transmission
SeeClutch brakeandDouble clutch proceduresin theClutchsection
of this chapter.
Clutch
Do not ride or slip the clutch as this causes unnecessary heat and wear.
Maintain the specified clutch adjustment to prolong its life and regularly
inspect the clutch control linkage for tightness. See theScheduled
Maintenancechapter for other maintenance information. When
adjustment of the clutch is necessary, it is very important that the work
be performed properly or early clutch failure may result and a costly
clutch overhaul may become necessary. Only a qualified technician
should perform clutch work.
Note:Continued use of a damaged or worn clutch, prolonged clutch
slippage or downshifting at excessive speeds can result in a failure of the
engine, transmission or clutch components.
Note:To avoid premature clutch wear and failure, do not drive with
your foot resting on the clutch pedal or use it to hold your vehicle at a
standstill on an upgrade as when waiting for a traffic light.
Engaging the Clutch
•Always start in the proper gear. An empty vehicle can start in a
higher gear than a fully loaded vehicle. Starting in too high a gear can
cause clutch slippage and excessive heat and wear on the clutch. A
gear that starts the vehicle moving at idle speed is the correct gear. If
you have to rev the engine to get your vehicle going, the gear
selection is too high.
•Do not shift until your vehicle has reached the proper speed.
Upshifting before your vehicle has reached the proper speed can
cause clutch slippage and excessive heat and wear on the clutch.
•Never hold a vehicle on a grade with the clutch. This causes the
clutch to slip and can actually burn up the clutch.
•Never coast with the clutch disengaged. The high RPM (sometimes
over 10000) can actually burst the facing material of the clutch.
•Never engage the clutch while coasting. Re-engaging the clutch after
coasting may not only cause a great shock to the clutch, but the
whole drivetrain. Internal engine damage or clutch and flywheel
failure can result from this.
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If the transmission is equipped with a ceramic clutch, you must start
your vehicle moving in first gear and engage the clutch before pressing
the accelerator at idle. In addition, do not try to slip the clutch by raising
engine RPM and riding or feathering the clutch pedal since this causes
erratic engagement that can cause engine stalling and potential serious
damage to driveline components.
Clutch Brake (Non-Synchronized Transmissions) - Vehicle
Stationary
A clutch brake stops transmission input shaft rotation so you can
accomplish the initial first gear or reverse gear selection when your
vehicle is stationary and the engine is at idle speed. Clutch brake
application occurs in the last 1 inch (25 millimeters) of clutch pedal
travel.
When using the clutch brake, fully press the clutch pedal and shift the
transmission into first gear or reverse. If the transmission does not go
into one of these gears, slowly release the clutch pedal while applying
light pressure on the transmission shift lever until it shifts into gear.
Note:After engagement of first gear, do not use the clutch brake for
upshifting or downshifting. If you do, clutch brake life shortens and gear
selection shift efforts may increase.
Double-Clutch Procedures - Non-Synchronized Transmissions
In order to properly upshift or downshift:
1. Press the clutch pedal to disengage the clutch.
2. Shift the transmission into neutral.
3. Release the clutch pedal.
If upshifting, wait until the engine speed matches the transmission speed
of the gear you are selecting.
If downshifting, accelerate the engine until the engine speed matches the
input speed of the gear you are selecting. Press the clutch pedal
immediately and shift into the desired gear, then release the clutch
pedal.
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Allison 3000 Series Push-Button Shifter
To shift to Reverse or Drive:
1. Press the brake pedal.
2. Press R or D on the shifter.
3. Release the brake pedal.
To select a higher range when in Drive,
press the up arrow button.
To select a lower range when in Drive,
press the down arrow button.
To place the transmission in Neutral, press
N.
Allison 3000 Prognostics
This transmission is equipped with the Allison Prognostics feature that
can alert the driver to needed transmission maintenance and
transmission fluid and filter life. See the separate Allison transmission
manual for complete details.
POWER TAKE-OFF (PTO) OPERATION (IF EQUIPPED)
A PTO unit allows the transmission to power auxiliary equipment to run
devices such as snowplows, aerial lifts, tow truck lifts, cement mixers or
dump trucks.
Vehicles Equipped with an Allison Automatic Transmission (Except
3000 Series)
You can operate the PTO while your vehicle is standing or moving. To
engage the PTO, apply the brakes and shift to any gear other than
positionN,then engage the PTO.
If the gear teeth not meshing properly prevent engagement, release the
brakes and allow your vehicle to creep slightly or shift the selector to
positionNand then back into gear. Never engage the PTO by clashing
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You can lock and unlock the differential when your vehicle is moving at a
constant speed of less than 25 mph (40 km/h) and while the wheels are
not slipping. Do not lock the differential when your vehicle is traveling
down steep grades and traction is minimal.
The differential lock and differential lock light automatically disengage at
speeds above 25 mph (40 km/h). The differential lock remains off until
either you restart your vehicle or you turn the differential lock switch off
then back on.
Turn the engine off and raise all drive wheels of the locker differential
axle in order to prevent your vehicle from moving when servicing the
wheels, tires or brakes. Axles equipped with a NoSPIN Detroit Locker
differential 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.
Take care 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.
Fluid Temperature
Axle operating temperatures normally do not exceed 100°F (38°C). If
the operating temperature exceeds 230°F (110°C), the rate of axle
lubrication oxidation increases and shortens the life of the lubricant and
seals, requiring axle lubrication changes to become more frequent to
preserve the axle. Do not consistently run extreme pressure (EP)
lubricants above 230°F (110°C).
Axle Conversions
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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GENERAL INFORMATION
All standard equipment brakes self-adjusting. Automatic adjustment,
when required, occurs whenever you apply and release the brakes during
forward or reverse operation.
Note:Occasional brake noise is normal. If a metal-to-metal, continuous
grinding or continuous squeal sound is present, this may indicate worn
brake linings. Have them inspected by an authorized dealer. If your
vehicle has continuous vibration or shudder in the steering wheel while
braking, an authorized dealer should inspect the vehicle.
Know the required stopping distances for all driving conditions you may
encounter. For longer brake lining life, take full advantage of engine
braking power when coming to a stop.
WARNING:Do not drive with your foot resting on the brake
pedal. This results in abnormally high brake temperatures,
excessive lining wear and increased stopping distances.
Before descending a long or steep hill, shift to a lower gear and avoid
continuous application of the brakes. Normally, choose the same gear to
descend the hill that you use to ascend the hill.
WARNING:Continuous application of the brakes causes the
brakes to overheat, resulting in a temporary loss of braking.
See theInstrument Clusterchapter for information on the
brake system warning light.
Wet brakes result in reduced braking efficiency. Gently press the brake
pedal a few times when driving from a car wash or standing water to dry
the brakes.
If Brakes Do Not Grip Well
•If you have been driving through deep water, gently apply the brakes
several times while your vehicle is moving slowly.
•Let the brakes cool if you have been using them excessively, as in
mountain driving or after several fast, high-speed stops.
•Check brake adjustment.
•Check brake linings for excessive wear.
•Check system air pressure on vehicles equipped with air brakes.
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Anti-lock Brake System (ABS)
This system helps you maintain steering control during emergency stops
by keeping the brakes from locking.
The ABS lamp momentarily illuminates when you switch on the
ignition. If the light does not illuminate during start-up, if it
remains on or flashes, the ABS may not be working and
requires servicing.
If the ABS is disabled, normal braking is still effective. If the
brake warning lamp illuminates, have your brake system
serviced immediately.
If you connect a PLC trailer with the ignition on, the trailer
ABS light also illuminates. If the light fails to illuminate, if it
remains on after you start the vehicle or continues to flash,
have the system serviced immediately.
FULL POWER BRAKE SYSTEM
WARNING:If the red BRAKE warning lamp in the instrument
cluster remains illuminated after engine start up, this indicates a
system failure in the Full Power Brake System. Stop the vehicle safely
as soon as possible and seek service immediately.
This system incorporates standard braking, an anti-lock braking system
(ABS) and optional Power Park Brake into one fully integrated hydraulic
brake system. With the Full Power Brake System, braking energy is
stored, similar to an air brake system, resulting in faster response times
and shorter stopping distances. This is accomplished using motor and
pump assemblies that pressurize the system by pumping brake fluid into
accumulators. This is similar to the air compressor of an air brake system
pressurizing the air tanks. The system includes a master cylinder that
provides the normal pedal feel and transfers the pedal force, via brake
fluid, to the main components of the system.
Note:The motor and pumps run momentarily with the ignition switch in
the on or run position, or in the off position with the brake pedal
pressed.
Note:During normal driving, you may hear the pump and motors
replenishing the accumulators. This is a normal function of the system.
AIR BRAKES
After starting the engine, give the air compressor time to build up the air
pressure to 60 psi (414 kPa) before moving your vehicle.
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WARNING:Do not drive or continue to drive if the low air
pressure buzzer is sounding or the brake warning light is lit.
These warnings indicate that air pressure is not to normal operating
level. Continued use of the vehicle could result in loss of braking ability.
WARNING:Avoid repeated light application of the brake pedal.
This depletes air pressure faster and could result in loss of
braking capability.
Periodically check the air pressure
gauge while driving. Pressure should
range between approximately
100–125 psi (690–862 kPa). The air
compressor governor cut-in and
cutout pressure settings are set at
the factory and are not adjustable.
When air pressure is insufficient (below 60 psi [414 kPa]), a
warning light illuminates and a buzzer sounds when the ignition
is in the on position.
This may happen because excessive brake applications are depleting the
system air pressure. If this condition occurs, stop driving your vehicle
until the compressor has fully recharged the air system.
WARNING:Do not move the vehicle when the air pressure is
insufficient because the brake system may be inoperative.
Select a gear ratio to help slow your vehicle before descending grades.
Supplementing with brakes, as required, help to safely slow the vehicle
and avoids overspeeding the engine.
Air Chamber Stroke Indication
Air chamber push rods have orange stroke indicator markers that warn
when the braking system requires adjustment or repair. The painted
orange indicator is on the air chamber push rod at the slack adjuster
stroke dimension that requires service when visible during brake
application.
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A switch on the instrument panel,
in combination with the accelerator
and clutch pedal, allows the
operator to make maximum use of
the exhaust brake in the following
conditions:
•Off-highway driving
•Mountain driving
•Heavy traffic
•High-speed highway driving.
To switch the brake on, push the switch up. Push the switch down to
turn it off.
While approaching a steep grade, make sure that the exhaust brake
switch is in the on position. The exhaust brake begins working as soon as
you remove your foot from the accelerator pedal.
Before descending a hill or steep grade, always select the proper gear. If
you take the transmission out of gear while descending, it is possible that
you cannot select another gear because of maximum governed RPM.
Make sure the engine speed does not exceed the maximum allowable
engine RPM. Exceeding the maximum allowable engine RPM can result
in damage to the engine. Apply the service brakes to reduce the engine
RPM or make a slower descent by using a lower gear.
While going down the grade, use a low enough gear to descend safely
with a minimum application of the service brakes. As a general guideline,
use the same gear as you use to ascend the hill.
Exhaust Brake Operating Characteristics
The exhaust brake turns on when you remove your feet from both the
accelerator and clutch pedals and the exhaust brake switch is in the on
position. The following conditions exist if the brake is operating properly:
•A slight change in engine sound when the exhaust brake turns on.
•A smooth braking effect. Do not expect a retarding effect similar to
sudden, hard application of the service brakes.
•The retarding force possibly felt acting against your body during
brake application (depending on the grade and vehicle load). This
force is actually preventing the vehicle from going much faster.
•Engine temperature remaining in the normal operating range.
•The tachometer showing a drop in engine RPM (depending on grade
and vehicle load) during a descent.
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