Brake-shift Interlock
Vehicles equipped with a gasoline engine have a brake-shift interlock
feature that prevents you from moving the gearshift lever from position
Pwhen the ignition is in the on position and the brake pedal is not
pressed.
If you cannot move the gearshift lever out of positionPwith the ignition
in the on position and the brake pedal pressed, it is possible that a fuse
has blown or your vehicle’s brake lamps are not operating properly. See
theFuseschapter.
WARNING:Do not drive your vehicle until you verify that the
brake lamps are working.
WARNING:When doing this procedure, you will be taking the
vehicle out of park which means the vehicle can roll freely. To
avoid unwanted vehicle movement, always fully set the parking brake
prior to doing this procedure. Use wheel chocks if appropriate.
WARNING:If the parking brake is fully released, but the brake
warning lamp remains illuminated, the brakes may not be
working properly. See your authorized dealer.
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Position P
This position locks the transmission and prevents the rear wheels from
turning.
To put your vehicle in gear:
1. Start the engine.
2. Press the brake pedal.
3. Move the gearshift lever into the desired gear.
To put your vehicle in positionP:
1. Come to a complete stop.
2. Move the gearshift lever and securely latch it in positionP.
Position R
With the gearshift lever in positionR,your vehicle moves backward.
Always come to a complete stop before shifting into and out of position
R.
Position N
With the gearshift lever in positionN,you can start your vehicle and it is
free to roll. Hold the brake pedal down while in this position.
Position D
This is the normal driving position for the best fuel economy. This
position allows automatic upshifts and downshifts in gears one through
six.
Position 4
This position allows automatic upshifts and downshifts in gears one
through four.
Position 2
Use this position to start-up on slippery roads or provide extra engine
braking on downgrades.
PRND 4 2 1
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Allison 2500
WARNING: To avoid sudden, unexpected vehicle movement
and possible personal injury or death:
1. Bring the vehicle to a complete stop.
2. Shift the transmission into positionN.
3. Apply the parking brake and make sure it is holding properly.
4. Turn the engine off when you leave the vehicle.Never leave the
vehicle unattended when the engine is running.
This transmission is available with a column-mounted gearshift lever. The
instrument cluster displays the gear positions.
Allison 3000
Note:For more information about this transmission, see the separate
Allison 3000 Series Operator’s Manual.
The Allison 3000 series offers two shift modes: Performance and
Economy.
Performance mode gives the best all-around transmission operation. The
transmission defaults to this mode when you start the engine. Pressing
MODE on the shifter switches to Economy mode and illuminates the
Mode ON lamp.
Economy mode provides operation at lower engine RPM while
maintaining adequate performance.
If the engine speed is above idle when a gear is selected using the
shifter, the vehicle does not move; the shifter must be moved to re-select
a gear after the engine speed returns to idle.
Torque Lock
If you park your vehicle on an incline without properly engaging position
P(by shifting into positionPbefore applying the parking brake), the
weight of the vehicle may generate an excessive amount of torque on the
parking pawl. This makes it difficult to shift the transmission out of
positionP.Hold the brake pedal down while shifting out of positionP,
then release the parking brake.
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To engage the PTO unit, stop your vehicle, place the transmission in
positionN.Press the clutch, and allow the gears to stop rotating, and
then engage the PTO unit. You can also select the PTO with the
transmission in gear as long as the clutch is pressed.
When operating the PTO with your vehicle stationary, first set the
parking brake (chock the wheels if your vehicle is on a hill or another
uneven surface).
REAR AXLES
Gross Axle Weight
WARNING:Exceeding these ratings by overloading can cause
component failure resulting in property damage, personal injury
or death.
Your truck has gross axle weight, gross vehicle weight and gross
combination weight ratings. Do not exceed these ratings.
Locking or Limited-Slip Differentials
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
If your vehicle is equipped with a locking or limited-slip differential, note
the following:
•Power is 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 your vehicle stationary.
Driver-controlled Differential Lock
Note:Never use the differential lock at vehicle speeds above 25 mph
(40 km/h).
Some drive axles have a driver-controlled differential lock. The
differential lock can lock or unlock the differential when your vehicle is
moving or stopped. When extra traction is required, the differential lock
provides full power to both axles.
When you lock the differential, your vehicle’s turning radius increases
(under-steer).
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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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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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HINTS ON DRIVING WITH ANTI-LOCK BRAKES
When the system is operating, the brake pedal pulses and may travel
further. Maintain pressure on the brake pedal. You may also hear a noise
from the system. This is normal.
The ABS does not eliminate the dangers inherent when:
•You drive too closely to the vehicle in front of you.
•Your vehicle is hydroplaning.
•You take corners too fast.
•The road surface is poor.
EXHAUST BRAKE (IF EQUIPPED)
WARNING:The exhaust brake is not recommended for use on
slippery or low traction road surfaces. Under these conditions a
loss of vehicle control could occur.
Note:Installing an exhaust or auxiliary brake does not necessarily
protect the engine from exceeding maximum governed speed. Use the
primary brakes to make sure the engine never exceeds maximum
governed speed under any conditions.
Note:Before starting the engine, make sure that the exhaust brake
switch is in the off position. Do not turn the exhaust brake on until the
engine has reached normal operating temperature.
Note:Maximum exhaust brake performance relates to the type of
transmission your vehicle has.
Note:Engine speed has a major influence of retarding performance.
When engine speed is stays at the maximum allowable level, the exhaust
brake operates at peak performance.
Note:Manual transmissions should be downshifted to the lowest gear
possible, without exceeding the maximum RPM limit of the engine. This
maximizes the exhaust brake’s retarding effect.
Note:Exhaust brakes operate effectively with automatic transmissions,
but performance varies with engine speed and the gear selected by the
transmission.
An exhaust brake is an auxiliary braking system that assists, but does
not replace, the primary service brake system. It helps control vehicle
speed; it is not a vehicle-stopping device.
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Actuation of Trailer Park (Emergency) or Tractor Bobtail Position
To actuate the trailer brakes only, pull out the trailer air supply knob
(A). This applies the trailer brakes whether the trailer uses emergency
or spring brakes.
You can also use this mode when the tractor or truck with trailer is used
during bobtail operation.
PARKING BRAKE
Hydraulic Brakes
WARNING:Do not use the gearshift selector in place of the
parking brake. Always set the parking brake fully AND make sure
the gearshift selector is in positionRfor vehicles equipped with a
manual transmission or positionP (if equipped)orNfor vehicles
equipped with an automatic transmission. Use of wheel chocks is also
recommended in hilly or off-road usage. Unexpected and possible
sudden vehicle movement may occur if these precautions are not taken.
WARNING:If the parking brake is fully released but the parking
brake warning lamp remains illuminated, the brakes may not be
working properly. See your dealer or a qualified service technician.
Apply the parking brake whenever the vehicle is parked. To set the
parking brake, pull the handle up until it snaps into the locked position.
When the parking brake is out of adjustment, seek service immediately.
The parking brake warning lamp in the instrument cluster
illuminates, and remains illuminated (when you switch on the
ignition), until you release the parking brake.
B
A
P
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