Manual High Idle System
If your vehicle has this
feature, the manual high
idle switch is located in
the instrument panel
switchbank.
This system can be used to increase your engine idle
speed whenever the following conditions are met:
•The brake pedal is not pressed.
•The vehicle speed is below about 5 mph (8 km/h)
for vehicles with diesel engines. The vehicle must
not be moving and the accelerator must not be
pressed for vehicles with gasoline engines.
•The manual transmission (if equipped) clutch pedal
is not pressed or, the automatic transmission
(if equipped) is in NEUTRAL (N) or PARK (P).The manual high idle feature is activated by pressing
the switch on the instrument panel. When the switch is
pressed again, or any of the previous conditions are
not met, manual high idle will be deactivated.
The manual high idle has been preset at the factory.
Your dealer may change the setting to fit your needs.
For vehicles with Caterpillar
®diesel engines, manual
high idle can be used to set any desired high idle speed.
To set a new temporary engine idle speed do the
following:
1. Make sure all of the previously described
conditions are met.
2. Press the accelerator pedal to the desired
engine speed.
3. Momentarily press the manual high idle switch.
The temporary high idle speed will be set. This new high
idle rpm level will be remembered by the system until
either the ignition is turned to OFF or a new high idle
speed is set.
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The high idle speed will be temporarily interrupted and
the engine speed will return to normal if any of the
following conditions occur:
•The brake pedal is applied.
•The accelerator pedal is pressed.
•The automatic transmission is shifted out of
PARK (P) or NEUTRAL (N).
•The clutch pedal on the manual transmission is
pressed.
•Vehicle speed is detected.
Once these inputs are removed, the engine idle speed
will slowly ramp back up to high idle after the normal
delay, if the conditions for engine coolant temperature
and air intake temperature are still met.
If this feature is turned off, by doing the brake stomp
procedure described above, and then the engine
is started the exhaust brake/restrictor light will flash for
10 seconds and then it will turn off.
Engine Checks Before Operating
When you have started your engine, let it run for
20 to 30 seconds before you put a load on the engine.
But do not leave the vehicle while the engine is running.
Avoid unnecessary idling of diesel engine equipped
vehicles.
If the engine idles too long, the temperature of the
engine coolant will fall below the normal operating
range. Low engine operating temperature causes
several conditions which affect engine operation and
reduce engine life.
The engine should be permitted to go through a
warm-up period. Operate the vehicle at a minimum of
600 rpm during the warm-up period. During this
period and during operation, the following observations
should be made.
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Diesel Engine Exhaust Brake
If your vehicle is equipped with a diesel engine,
it may have an exhaust brake, which is located in the
exhaust system.
The exhaust brake is used to help slow the vehicle and
may assist the vehicle’s foundation brakes. The use of
the exhaust brake will assist the braking of the vehicle
and prolong the life of the foundation brake lining
material.
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 will come on when the
exhaust brake is active. SeeExhaust Brake Indicator
Light on page 3-40for more information.When using the exhaust brake, the proper gear range
selection is important. The exhaust brake will be
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 a DURAMAX®7800 diesel
engine, do not exceed 2550 rpm. If you have a
DURAMAX
®6600 diesel engine, do not exceed
3600 rpm.
If you have an Allison
®1000/2000/2200/2400/2500
series automatic transmission and press this button,
the transmission will downshift to a factory default
setting of fourth gear. To change the default setting,
or for more information on factory default settings,
contact your dealer for assistance.
The accelerator and clutch pedals must be released in
order for the exhaust brake to engage. The exhaust
brake will not function when the cruise control feature
is active with a DURAMAX
®6600 engine, and will
automatically shut off when the anti-lock brake system
is active.
When equipped with a Caterpillar
®diesel engine,
the exhaust brake will become active in cruise control
when you exceed the set speed by 3 mph.
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Two-Speed Rear Axle Electric
Shift Control
If your vehicle is equipped with this feature, you will find
a label on the headliner above the windshield or in
another place near the driver that shows how to use it.
Be sure to follow the directions carefully.
Use the following directions based on the type of shift
control you have.
The rear axle shift control
switch for a manual
transmission is located
on the shift lever.When the switch is up, the rear axle is in the high
range. Push the switch down to change to low range.
The two-speed axle should be in low when you park
the vehicle. You will need to engage the transmission,
even move the vehicle a little, to be sure the axle is
in the low range. Then apply the parking brake, shift into
NEUTRAL and shut off the engine.
Also, always start the vehicle in motion with the
two-speed axle in the low range. To shift up from low
to high, do the following:
1. Move the switch up for the high range,
2. disengage the clutch, and
3. after a brief pause, engage the clutch and then
press down on the accelerator.
To shift down from high to low, do the following:
1. Move the switch down to low,
2. release the accelerator and then quickly
apply it again.
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Air Shift Control
(Automatic Transmission)
The rear axle shift control
switch for an automatic
transmission is located in
the instrument panel
switchbank.
Press the bottom of the switch to get to the low range.
The switch indicator light will come on when the
vehicle is in low range. Press the top of the switch to
return to the high range.
The two-speed axle should be in low range when you
park the vehicle. You will need to engage the
transmission, even moving the vehicle a little, to be sure
the axle is in low range. Then shift into PARK (P),
apply the parking brake and shut off the engine.To shift up from low to high, press the top of the rear
axle shift control switch and press down on the
accelerator. When you shift the axle from high to low,
press the bottom of the switch, release the accelerator
and then quickly press it down again.
To operate off-road or under a heavy load, shift into
low range when the vehicle is standing still and
then operate the transmission normally.
On the highway, with the axle in low range and the
transmission in top gear, you may shift the axle to
high range by raising the switch and releasing
the accelerator momentarily. Re-apply the accelerator
after you shift.
Under light load conditions, first shift the axle into the
high range with the vehicle at a standstill and then
operate the transmission normally.
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Automatic Transmission Operation
We build vehicles with Allison®five and six-speed
automatic transmissions. This part of the manual covers
the basics of these. With these transmissions, you
will find another Allison
®manual in your vehicle that
goes into more detail. On the headliner, in front of and
above the driver, or in some other place near the
driver, you will see a label that describes important
operating facts about the automatic transmission in
your vehicle. Make sure you follow the instructions on
this label.
Be sure to keep your parking brake set until you are
ready to shift into DRIVE (D), and press the brake pedal
while shifting from NEUTRAL (N) or PARK (P) to a
drive gear.
All vehicles equipped with automatic transmissions can
be started in PARK (P), if equipped, or in NEUTRAL (N).
See the Allison
®Transmission Operator’s Manual in
your vehicle for more information about this.
{CAUTION:
It can be dangerous to get out of your vehicle
without the parking brake rmly set. Your
vehicle can roll. If you have left the engine
running, the vehicle can move suddenly. You or
others could be injured. To be sure your vehicle
will not move, even when you are on fairly level
ground, always set the parking brake.
{CAUTION:
Shifting into a drive gear while your engine is
running at high speed is dangerous. Unless
your foot is rmly on the brake pedal, your
vehicle could move very rapidly. You could
lose control and hit people or objects. Do not
shift into a drive gear while your engine is
running at high speed.
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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 will come on whenever overdrive defeat is active.
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 your vehicle.
Double-Clutching
You must use the double-clutching method when you
shift an unsynchronized gear set. Disengage the clutch,
shift to 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.
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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
FIRST (1) 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.
ZF Six-Speed Transmission
Here is how to operate your transmission.
This six-speed pattern is
unique to GM manual
transmissions.
The transmission always repositions the shift lever to
NEUTRAL, which is located between FOURTH (4)
and FIFTH (5) gear.
To prevent unintentional gear selections, additional force
is required to move the shift lever into REVERSE (R) or
FIRST (1). Use FIRST (1) when trailer towing, driving
with a heavier payload or launching on a grade.
Otherwise, start in SECOND (2) gear. Only shift into
FIRST (1) when the vehicle has stopped moving.
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