
Exhaust Restrictor (Engine
Warm-Up)
Exhaust Restrictor
If the vehicle has a Isuzu 6H Diesel Engine, it may have
a feature called an Exhaust Restrictor (NPE), which
uses an air actuated valve in the exhaust system
to restrict exhaust gas flow which enhances the engine
and heater warm-up.
Automatic Quick Warm-Up
If the vehicle has a DURAMAX®6600 engine, it has a
feature called an Automatic Quick Warm-Up, which uses
the turbocharger to restrict the exhaust gas flow
which enhances the engine and heater warm-up.
In both systems, exhaust restrictor or automatic quick
warm-up, the cold temperature high idle feature elevates
the engines idle speed, up to 1500 rpm, and restricts
the exhaust gas flow, when outside temperatures
are below 50°F (10°C), and the engine coolant
temperature is below certain levels. This feature
enhances heater performance by raising the engine
coolant temperature faster.For all engines this feature is already turned on. The
automatic quick warm-up on the DURAMAX
®engine
can be turned off and on by doing the following
procedure:
1. Turn the ignition to ON/RUN, with the vehicle off.
2. Press the accelerator pedal to the floor and
hold it while quickly pressing and fully releasing the
brake pedal three times in less than eight seconds.
3. Release the accelerator pedal and start the engine.
The green exhaust brake/restrictor light below the
radio controls will be lit for 10 seconds.
If this feature is turned off, by doing the procedure
described previously, and then the engine is
started, the exhaust brake/restrictor light will flash
for 10 seconds and then it will turn off.
When the engine is started, it will slowly increase to the
high idle speed after a delay of a few seconds; up to
about two minutes. For this method to work properly
there must be no throttle or brake pedal faults, and the
throttle pedal must not fall below 75 percent of wide
open throttle while pressing the brake pedal.
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During this warm-up period, check the warning lights
and gages:
•If oil pressure does not begin to rise within
15 seconds of starting, stop the engine and find the
cause. SeeOil Pressure Gage on page 3-38for
more information.
•If the engine coolant temperature gage needle goes
into the hot area on the gage, stop the engine and
find the cause of the overheating. SeeEngine
Coolant Temperature Gage on page 3-34for more
information.
•If you have air brakes, the dual-needle air pressure
gage should read at least 115 psi (790 kPa) for both
service systems before you try to move the vehicle.
When air pressure is below 60 psi (420 kPa), the
LOW AIR light will come on and you will hear a
tone alarm. SeeBrake System Warning Light on
page 3-31for more information. If the pressure does
not build up or drops during warm-up, stop the
engine and find the cause before you try to move the
vehicle. Recommended air pressure before driving is
120 psi (830 kPa). SeeAir Pressure Gage on
page 3-47for more information.
•The charging system light should come on when the
ignition key is turned to ON/RUN or START and
should go out when the engine is running above idle.
If the light does not go out or comes back on during
normal engine operation, have the charging system
checked right away. (This light tells you if the
generator is not charging; it does not reflect the
condition of the battery.) SeeCharging System Light
on page 3-29for more information.
•The voltmeter charge indicator gage tells you the
condition of the battery’s charge. The gage should be
in the center area during engine operation. The red
area on the left indicates an undercharge condition;
the red area on the right indicates an overcharge.
If the gage is in either red area, have the battery and
charging system checked right away. SeeVoltmeter
Gage on page 3-30for more information.
Notice:Do not allow the engine to operate at low
idle for more than five minutes. This can cause low
engine operating temperatures which can affect
engine operation and reduce engine life. Engine idle
speed should be increased to 1200 rpm whenever
extended idle is required. Once started, the engine
should be placed under load to allow the engine
coolant temperature to reach 150°F (66°C) before
shutting off the engine.
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Diesel Engine Exhaust Brake
If the vehicle has a Isuzu 6H Diesel Engine, it may have
an exhaust brake, which is located in the exhaust
system.
If the vehicle has a 6.6L DURAMAX
®6600 or
Caterpillar®Diesel Engine, it may have an exhaust
brake, which is controlled through the turbocharger.
The exhaust brake for both engines operates the same.
The exhaust brake switch
is located in the instrument
panel switchbank.
Push the bottom of the switch to turn the exhaust brake
on. When you push the top of the switch, the exhaust
brake will turn off.
There is an indicator light on the instrument panel
similar to the symbol on the switch, that comes on when
the exhaust brake is active. SeeExhaust Brake
Indicator Light on page 3-41for more information.While using the exhaust brake, the proper gear range
selection is important. The exhaust brake is most
effective if the gear range selected is the lowest possible
range that does not allow the engine rpm to go more
than 200 rpm above rated (full load) rpm. If you have
a Caterpillar
®Diesel Engine, do not exceed 2900 rpm.
If you have an Isuzu 6H Diesel engine, do not
exceed 2550 rpm. If the vehicle has a DURAMAX
®
6600 Diesel Engine, do not exceed 3600 rpm.
If the vehicle has an Allison
®1000/2200/2300/2350/2500/
2550 series automatic transmission and this button is
pressed, the transmission downshifts to a factory default
setting of third gear. To change the default setting, or for
more information on factory default settings, contact your
dealer/retailer for assistance.
The accelerator and clutch pedals must be released in
order for the exhaust brake to engage. The exhaust
brake will automatically shut off when the antilock brake
system is active.
If the vehicle has a Caterpillar
®Diesel Engine or a
DURAMAX®6600 Diesel Engine, the exhaust brake will
become active in cruise control when you exceed the
set speed by 3 to 5 mph.
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Overdrive Defeat
If your vehicle has this feature, you can select not to
shift up to fifth gear. This is useful when towing or under
a heavy load.
The overdrive defeat
switch is located in the
instrument panel to
the right of the steering
column.
Press the switch to limit the transmission to fourth gear.
This will allow for fewer downshifts while pulling a
trailer or under a heavy load. The indicator light in the
switch comes on whenever overdrive defeat is active.
If the vehicle is equipped with a push button shift
selector, refer to the Allison
®Transmission Operator’s
Manual for shift selector operating instructions.
Manual Transmission Operation
Using the Clutch
When you are starting to move the vehicle, it is
important to begin with the engine speed at idle. Then
start to engage the clutch and listen for an engine speed
drop of about 100 rpm. At this point, the clutch is
engaging, so you should increase the engine speed and
fully engage the clutch. It is important not to increase
the engine speed sooner or before the clutch begins its
engagement. If you do, you can cause damage to
the vehicle.
Double-Clutching
You must use the double-clutching method when you
shift an unsynchronized gear set. Disengage the clutch,
shift to N (Neutral) and engage the clutch. When
upshifting, slow the engine until the engine rpm and
road speed match. When downshifting, accelerate the
engine until the engine rpm and road speed match. Then
quickly disengage the clutch and move the shift lever
to the next gear position and engage the clutch.
2-28

Eaton®Fuller®Five and Six-Speed
Transmissions and TTC Spicer
Seven-Speed Transmissions
These transmissions have gears that automatically
synchronize when you shift up or down (except 1 (First)
gear on the five-speed and seven-speed transmission
which is unsynchronized). Choose the gear that will
maintain the road speed you want while keeping
the engine above two-thirds of the governed speed.
When the engine speed drops below two-thirds of the
governed speed, shift into the next lower gear before
your engine begins to lug. When you shift down, be sure
to double-clutch if required.
Eaton®Fuller®Nine and Ten-Speed
Non-Synchronized Manual
Transmissions
If the vehicle has one of these transmissions the engine
rpm and road speed must match when upshifting and
downshifting. The label above the windshield will tell you
the operating basics you need to know.
The following are driving tips.
•Always choose an initial starting gear suitable for
the load and terrain.
•Always use double-clutching procedures when
shifting.
•Never move the range shift lever to the LO speed
gear position after HI range preselection, or
anytime the transmission is in the HI range.
•Never move the range knob or lever with the shift
lever in N (Neutral) while the vehicle is moving.
•Never make a range shift while moving in
R (Reverse).
Clutch Brake (Vehicles with
Non-Synchronized Transmission)
A clutch brake is used to stop transmission input shaft
rotation so that 1 (First) or R (Reverse) gear selection
can be initiated when the vehicle is at a standstill
and the engine is idling.
Press the clutch pedal all the way down to the floorboard
to apply the clutch brake.
When using the clutch brake, disengage the clutch pedal
and shift the transmission into either the initial starting
gear or R (Reverse). If the tooth-butting occurs between
the clutching teeth, re-engage the clutch while applying
light pressure to the shift lever. This will provide for a
smooth shift into either 1 (First) or R (Reverse) gear.
Notice:Using the clutch brake for shifting into any
gear other than 1 (First) or R (Reverse) may cause
premature wear of the clutch brake and make gear
shift effort more difficult. Do not use the clutch brake
for shifting after engaging 1 (First) or R (Reverse).
2-29

Locking Hubs
Turn the dial of the hublock (A) from the FREE position
to the LOCK position to lock the front axle.
Turn the dial of the hublock (A) from the LOCK position
to the FREE position to unlock the axle.
You do not have to back the vehicle up to disengage
the hublocks.If the vehicle has
four-wheel drive, the
transfer case knob is
located to the right of the
steering wheel on the
instrument panel. Use this
knob to shift into and
out of four-wheel drive.
An indicator light shows you which position the transfer
case is in. The indicator lights come on briefly when
you turn on the ignition and one stays on. If the lights do
not come on, you should take the vehicle to your
dealer/retailer for service. An indicator light flashes while
shifting the transfer case. It will remain on when the
shift is complete. If for some reason the transfer case
cannot make a requested shift, it returns to the last
chosen setting. Hublock Dial Location
Hublock Dial
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Shifting Into Four-Wheel High
Turn the knob to four-wheel high. This can be done at
3 mph or less. The indicator light flashes while shifting.
It remains on after the shift is complete. Be sure to
lock the front hubs.
Shifting Into Two-Wheel High
Turn the knob to Two-Wheel High. This can be done at
3 mph or less.
Shifting Into Four-Wheel Low
To shift to Four-Wheel Low, the vehicle’s engine must be
running and the vehicle must be stopped or moving less
than 3 mph (5 km/h) with the transmission in N (Neutral).
The preferred method for shifting into Four-Wheel Low is
to have the vehicle moving 1 or 2 mph (1.6 to 3.2 km/h).
Turn the knob to Four-Wheel Low. You must wait for
the Four-Wheel Low indicator light to stop flashing and
remain on before shifting the transmission into gear.
Be sure to lock the front hubs.Notice:Shifting the transmission into gear before
the Four-Wheel Drive Low indicator light has
stopped flashing could damage the transfer case.
To help avoid damaging the vehicle, always wait for
the Four-Wheel Drive Low indicator light to stop
flashing before shifting the transmission into gear.
If you turn the knob to Four-Wheel Low while the
vehicle is in gear and/or moving, the Four-Wheel Low
indicator light flashes for 30 seconds and does not
complete the shift unless the vehicle is moving less than
3 mph (4.8 km/h) and the transmission is in N (Neutral).
After 30 seconds, the transfer case returns to the
setting last chosen. If the vehicle is in gear and moving
less than 3 mph (4.8 km/h), the transfer case shifts
to Four-Wheel High.
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Shifting Out of Four-Wheel Low
To shift from Four-Wheel Low to Four-Wheel High or
Two-Wheel High, the vehicle must be stopped or moving
less than 3 mph (5 km/h) with the transmission in
N (Neutral) with the engine running. The preferred
method for shifting out of Four-Wheel Low is to have
the vehicle moving 1 or 2 mph (1.6 to 3.2 km/h).
Turn the knob to Four-Wheel High or Two-Wheel High.
You must wait for the Four-Wheel High or Two-Wheel
High indicator light to stop flashing and remain on before
shifting the transmission into gear.
Notice:Shifting the transmission into gear before
the Four-Wheel High or Two-Wheel High indicator
light has stopped flashing could damage the transfer
case. To help avoid damaging the vehicle, always
wait for the Four-Wheel High or Two-Wheel High
indicator light to stop flashing before shifting
the transmission into gear.
If the knob is turned to Four-Wheel High or Two-Wheel
High while the vehicle is in gear and/or moving, the
Four-Wheel High or Two-Wheel high indicator light
flashes for 30 seconds. It will not complete the shift
unless the vehicle is moving less than 3 mph (5 km/h)
with the transmission in N (Neutral).
Shifting Into Neutral
Before shifting the transfer case to N (Neutral), first
make sure the vehicle is parked so that it will not roll.
1. Set the parking brake. SeeParking Brake (With
Hydraulic Brakes) on page 2-38orParking Brake
(With Air Brakes) on page 2-41for parking
brake apply procedure.
2. Start the vehicle.
3. Put the transmission in N (Neutral).
4. Shift the transfer case to Two-Wheel High.
5. Turn the transfer case knob all of the way past
Four-Wheel Low and hold it there for a minimum
of 10 seconds. The N (Neutral) indicator light
comes on.
6. Shift the transmission to R (Reverse) for
one second, then shift the transmission to D (Drive)
for one second.
7. Turn the ignition to OFF.
8. Place the transmission shift lever in P (Park).
9. Turn the ignition to LOCK.
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