2003 CHEVROLET C/K towing

2-17 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.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.
NOTICE:
If you ever need 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.

2-19
Starting the Diesel Engine
If you have a Caterpillar diesel engine, also refer to your
Caterpillar
Diesel Engine Operation & Maintenance
Manual for starting procedure.
For vehicles with the DURAMAX diesel engine, also
see ªStarting Your DURAMAX Diesel Engineº
following.
To make starting easier in cold weather (below 32F or
0C), the proper viscosity engine oil should be used.
See ªEngine Oilº in the Index. It's also best to heat the
engine oil first. You can do this by using an engine
coolant heater.
NOTICE:
If you ever need 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.
Restarting the Diesel 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 Diesel Engine
If you have a Caterpillar diesel engine, see your
Caterpillar
Diesel Engine Operation &
Maintenance Manual.
1. Set the parking brake and shift to NEUTRAL (N)
or PARK (P).
2. Turn the ignition key to OFF.
If your vehicle has a two
-speed axle, see ªRear Axle,
Tw o
-Speed Electric Shift Controlº or ªRear Axle,
Tw o
-Speed Airshift Controlº in the Index.

2-36 Overdrive Defeat (If Equipped)
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 better fuel economy and fewer
downshifts while pulling a tractor or 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'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 it's
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.

2-37 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's 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 payload in the pickup box or
launching on a grade. Otherwise, start in SECOND (2)
gear. Only shift into FIRST (1) when the vehicle has
stopped moving.

2-43
Vehicles built for use as tractors or towing vehicles have
two air brake controls. They look like this:To charge a trailer's air brake system do the following:
1. Move your tractor into the proper position.
2. Apply the parking brake by pulling the yellow
parking brake knob out.
3. Hook up the trailer air system properly.
4. Get into the tractor.
5. Push and hold down the regular brake pedal.
6. Push in both the yellow parking brake and the red
trailer air supply knobs. This will charge your
trailer's air system.
After a few minutes, the trailer system should be fully
charged. When it is, the air pressure gage will show
about 125 to 135 psi (862 to 931 kPa).
For driving with a trailer, the yellow and red
(if equipped) knobs must be pushed in. It's the same
when you're not pulling a trailer except that the red
trailer air supply knob must be pulled out.

2-44
CAUTION:
If you apply any one of the air brake parking
controls while the vehicle is moving, your rig will
stop suddenly. If you are not ready for this, you
or others could be injured. Don't apply any one
of these controls while you're driving, unless you
have to make an emergency stop.
If the air pressure drops below 60 to 70 psi (413 to
482 kPa), the primary brake light and warning buzzer
will come on. If the air pressure drops to 35 to 45 psi
(241 to 310 kPa), the red trailer air supply knob will
automatically pop out and apply the spring brakes on
the trailer.If the air pressure drops to 35 to 45 psi (241 to 310 kPa),
the yellow park brake knob will automatically pop out
and apply the spring brakes on the truck or tractor.
If you ever have a complete loss of air so that your air
brakes automatically apply, there is a way that the tow
operator can release the parking brakes to tow the
vehicle. See ªTowing Your Vehicleº in the Index.
CAUTION:
If your vehicle is left in gear, the engine can start
if the vehicle starts to roll. This can easily happen
if you have the diesel engine. Shift the
transmission into NEUTRAL (N) before you
leave the vehicle.

2-66
Certain electrical accessories may not be compatible
with the accessory power outlet and could result in
blown vehicle or adapter fuses. If you experience a
problem, see your dealer for additional information on
accessory power outlets.
NOTICE:
Adding some electrical equipment to your vehicle
can damage it or keep other things from working
as they should. This wouldn't be covered by your
warranty. Check with your dealer before adding
electrical equipment, and never use anything that
exceeds the amperage rating.
When adding electrical equipment, be sure to follow the
proper installation instructions included with the equipment.
NOTICE:
Power outlets are designed for accessory plugs
only. Do not hang any type of accessory or
accessory bracket from the plug. Improper use of
the power outlet can cause damage not covered
by your warranty.
Trailer Connections (C4/C5 Models
Only) (If Equipped)
Heavy-Duty Trailer Wiring Package
Your vehicle may be equipped with an eight-wire trailer
towing harness. This harness, with a seven
-pin universal
heavy
-duty trailer connector, is attached to a bracket on
the platform hitch.
The Center High
-Mounted Stoplamp (CHMSL) wire is
tied next to the trailer wiring harness for use with a trailer.

2-67
The eight-wire harness contains the following
trailer circuits:

Yellow: Left Stop/Turn Signal

Dark Green: Right Stop/Turn Signal

Brown: Taillamps

White: Ground

Light Green: Back
-up Lamps

Light Blue: CHMSL

Red: Battery Feed

Dark Blue: Trailer Brake
Trailer Connections (C6/C7/C8
Models Only) (If Equipped)
If your vehicle has these trailer connections, they are
located at the rear of the cab for a tractor and at the rear
of the chassis when towing a trailer. There will be an air
connection and an electrical connection.
Be sure that the couplings to the trailer are
made correctly.
Air Connections
If you are not connecting the trailer air line connections
to another piece of equipment, be sure to replace their
protective caps.
Electrical Connections
This system is a seven-wire cable that will connect to
the trailer, supplying power to the trailer's lighting
system. When not in use, it is stored in the trailer
air
-hose storage bracket.
NOTICE:
Starting in 1998, the center pin (also known as
the auxiliary circuit) of the seven
-pin trailer
electrical connector will be wired to provide
continuous power for the trailer anti
-lock brake
systems when the ignition key is in the on
position. Care should be taken to insure that
continuous power on this circuit will not cause
damage to the trailer electrical system.
Consult with the trailer manufacturer for the
proper operation and checking procedures for
the trailer anti
-lock brake systems.