1999 GMC C-SERIES clutch
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2-8 Manual Transmission
Set the parking brake, shift your gear selector to
NEUTRAL and hold the clutch pedal to the floor while
starting the engine.
Starter Motor Operation
1. The starter motor will disengage if you release
the key or the engine reaches a predetermined
engine speed.
2. To prevent overheating, the starter motor will
disengage after continuously operating for 15 seconds.
You must release the key from the start position to
re
-engage the starter.
3. The starter motor will not engage if the engine is
already running.
4. The starter motor will disengage if, after two
seconds, the starter pinion gear does not engage the
flywheel or there is no engine rpm signal from the
engine speed sensor.
Starting Your Engine
1. Without pushing the accelerator pedal, turn your
ignition key to START. When the engine starts, let
go of the key. The idle speed will go down as your
engine gets warm.
2. If the engine doesn't start in 10 seconds, push the
accelerator pedal all the way down and crank the
engine for five more seconds, unless it starts sooner.
3. If your engine still won't start (or starts but then
stops), it could be flooded with too much gasoline.
Wait 15 seconds to let the starter motor cool down.
Do Steps 1 through 3 again.
When the engine starts, let go of the key and the
accelerator pedal.
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2-9
NOTICE:
Your engine is designed to work with the
electronics in your vehicle. If you add electrical
parts or accessories, you could change the way
the engine operates. Before adding electrical
equipment, check with your dealer. If you don't,
your engine might not perform properly.
If you ever have to have your vehicle towed, see
the part of this manual that tells how to do it
without damaging your vehicle. See ªTowing
Your Vehicleº in the Index.
Gasoline Engine Warm-Up
When you've started your engine, let it run for 20 or
30 seconds to warm up before you put a load on
the engine.
Drive at moderate speeds for the first few miles,
especially in cold weather. Running a cold engine at
high speed can damage it.
Restarting the Gasoline Engine While
Moving (Automatic Transmission)
If you have to restart the engine while the vehicle is
moving, you'll first have to shift the automatic
transmission to NEUTRAL (N). This safety feature
prevents starting the engine when the transmission is in
a drive gear.
Stopping the Gasoline Engine
Let your engine idle for a few seconds before turning it
off after you have finished driving your vehicle.
If you shift to NEUTRAL (N), set the parking brake.
If you shift to PARK (P), the auto
-apply feature will set
the parking brake.
If your vehicle has a two
-speed axle, put the range
selector in LOW. To be sure the axle has shifted into
LOW, engage the clutch and transmission the vehicle
may move slightly when you do this.
While your engine is idling before you turn it off, you
can make a list of any operational or handling concerns
to give to responsible maintenance personnel so they can
handle them right away.
Moisture will condense in a fuel tank that is almost
empty if the vehicle is not run for a while, even just
overnight under some conditions. So, it's always best to
refuel your vehicle at the end of each run.
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2-12 Fast Idle System (Electronically Controlled
Caterpillar
Diesel and Gasoline Engines)
If your vehicle is equipped with an electronically
controlled diesel engine, it has both automatic and
manual fast idle capabilities.
Automatic Fast Idle System
(Caterpillar
Diesel Engine Only)
The automatic fast idle feature will engage whenever
you start your vehicle and the engine is below the preset
operating temperature. This will help decrease engine
warm
-up time.
Idle speed will then return to normal under any of the
following conditions:
The engine reaches the preset operating temperature.
The brake pedal is pressed.
The trailer brake hand lever (if equipped) is applied.
The manual transmission clutch pedal is pressed or,
the automatic transmission (if equipped) is shifted
from NEUTRAL (N) or PARK (P).
The vehicle speed exceeds approximately
10 mph (16 km/h).
When the fast idle switch is pressed a second time.Manual Fast Idle System
(Caterpillar
Diesel and Gasoline Engines)
The manual fast idle switch
is located on the lower
portion of the instrument
panel just to the left of the
steering wheel.
This system can be used to increase your engine idle
speed whenever the following conditions are met:
The brake pedal is not pressed.
The trailer brake hand lever (if equipped) is not applied.
The vehicle speed is below approximately
10 mph (16km/h).
The manual transmission (if equipped) clutch pedal
is not pressed or, the automatic transmission
(if equipped) is in NEUTRAL (N).
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2-17
The accelerator and clutch pedals must be released in
order for the exhaust brake to engage. Whenever the
exhaust brake is active, the light in the switch will be on.
Do not use the exhaust brake when running the engine at
idle during warm
-up or other extended periods.
Prolonged use of the exhaust brake during idling will
cause the engine to overheat.
CAUTION:
Be careful when using the exhaust brake or you
could lock the wheels and lose control of the
vehicle. Operators not familiar with an exhaust
brake should not use this brake on slippery
surfaces before learning to use it on dry surfaces.
If the vehicle's wheels begin to lock when using
the exhaust brake on slippery surfaces, switch the
exhaust brake off immediately. The exhaust
brake will turn off if the anti
-lock brake system
is activated.
Tw o-Speed Rear Axle Electric Shift
Control (If Equipped)
If your vehicle has this feature, you'll find a label (or
labels) on the ceiling above the windshield or in another
place near the driver that show how to use it. Be sure
to follow the directions carefully. Use the following
directions based on the type of shift control you have.
Automatic Transmission
The switch for the rear axle
shift control is on the shift
tower to the right of the
shift lever.
When the switch is up, the rear axle is in the high range.
Push it down to get the low range.
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2-18
The two-speed axle should be in low range when you
park the vehicle. Apply the parking brake, shift to
PARK (P) or NEUTRAL (N) and shut off the engine.
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
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 your 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.
Manual Transmission
The switch for the rear axle
shift control is on the shift
lever. When the switch is
up, the rear axle is in the
high range. Push it down to
get the low range.
The two
-speed axle should be in low when you park the
vehicle. You'll 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. When you upshift the
rear axle from low to high, move the switch up for the
high range, disengage the clutch, pause, engage the
clutch and then press down on the accelerator. When
you shift the axle down from high to low, you don't
have to clutch. Just move the switch down to low,
release the accelerator and then quickly apply it again.
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2-19 Air Shift Control
(Manual Transmissions Only)
The lever for the rear axle
shift control is either at the
lower right corner of the
instrument panel or on the
shift lever.
When the lever is moved to HI, the rear axle will be in
the high range. Switch it to LOW to get the low range.
The two
-speed axle should be in LOW when you park
the vehicle.
You'll need to engage the transmission, even moving 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 position. When you upshift
the rear axle from LOW to HI, move the lever to the
HI position, disengage the clutch, pause, engage the
clutch and then press down on the accelerator. When
you shift the axle down from HI to LOW, you don't
have to clutch. Just move the lever to LOW, release the
accelerator and then quickly press it down again.
Air Suspension (If Equipped)
Your vehicle may be equipped with the Hendrickson
HAS Series single
-axle air suspension which is designed
for single
-axle on-highway use. This feature is available
in the 19,000 lb. capacity and as a low profile option for
operations which require extra cubic capacity and a
reduced deck height.
With this air suspension system, the ride height is set
during vehicle assembly so that the vehicle has a constant
frame height. The system will then increase or decrease
air pressure in the air springs to maintain this height.
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2-22
Manual Transmission Operation
This part of the manual covers the basics of the manual
transmission. With some of the transmissions, you
will find another manual in your vehicle that goes into
more detail.
Using the Clutch
When you're starting to move the vehicle, it's 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's 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 ªdouble-clutchingº method when you
shift an unsynchronized gear set. Simply disengage the
clutch, shift to NEUTRAL (N) and engage the clutch.
When you're shifting down to a lower gear, accelerate
the engine speed while in NEUTRAL (N) to get ready
for the lower gear.
Eaton Fuller 5 and 6-Speed Transmissions
and Dana Spicer 7-Speed Transmissions
These transmissions have gears that automatically
synchronize when you shift up or down (except
FIRST (1) gear on the five
-speed transmission which is
unsynchronized). Choose the gear which 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 9 and 10-Speed
Manual Transmissions
If your vehicle has one of these unsynchronized
transmissions, it's naturally somewhat complicated.
The label above the windshield will tell you the
operating basics you need to know.
Before operating the vehicle with one of these
transmissions, be sure to read the Eaton Fuller
Transmission Driver Instructions Manual in your vehicle.
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2-23 Eaton Fuller Transmission with Clutch
Brake (Option)
Some vehicles have an optional clutch brake. It engages
when you push your clutch pedal all the way to the
floor. Use it when you shift into first or reverse gear.
Press the clutch pedal as far as it will go and then make
your shift. If the engagement isn't smooth when you
engage the clutch, press the clutch pedal in and then
immediately re
-engage it. Use the clutch brake only
with the engine idling and the vehicle standing still.
If you have this feature, see the Eaton Fuller
Transmission Driver Instructions Manual before
operating your vehicle.
Eaton Fuller Transmission with
Countershaft Brake (If Equipped)
The countershaft brake is used when you shift from a
standing start into FIRST (1) or REVERSE (R). You
will find this feature on vehicles with gasoline engines
and Eaton Fuller 9 or 10
-speed transmissions.
See the Eaton Fuller Transmissions Driver
Instructions Manual.
Parking
CAUTION:
If you don't park your vehicle properly, it can
roll. If you've left the engine running, it can move
very quickly. You or others could be injured.
To be sure your vehicle won't move, even when
you're on level ground, follow the steps below.
Two-Speed Rear Axle
1. With the engine running, shift the two-speed rear
axle into low. To be sure it's in low, you'll need to
move the vehicle in gear just a little.
2. Hold the regular brake pedal down with your
right foot.
3. Apply the parking brake.
4. Shift the transmission to NEUTRAL (N) or
PARK (P).
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