engine CHEVROLET C3500 HD 2002 4.G Service Manual

4-26 If You're Caught in a Blizzard
If you are stopped by heavy snow, you could be in a
serious situation. You should probably stay with your
vehicle unless you know for sure that you are near help
and you can hike through the snow. Here are some
things to do to summon help and keep yourself and
your passengers safe:

Turn on your hazard flashers.
Tie a red cloth to your vehicle to alert police that
you've been stopped by the snow.

Put on extra clothing or wrap a blanket around you.
If you have no blankets or extra clothing, make
body insulators from newspapers, burlap bags, rags,
floor mats
-- anything you can wrap around yourself
or tuck under your clothing to keep warm.
You can run the engine to keep warm, but be careful.

4-27
CAUTION:
Snow can trap exhaust gases under your vehicle.
This can cause deadly CO (carbon monoxide) gas
to get inside. CO could overcome you and kill
you. You can't see it or smell it, so you might not
know it is in your vehicle. Clear away snow from
around the base of your vehicle, especially any
that is blocking your exhaust pipe. And check
around again from time to time to be sure snow
doesn't collect there.
Open a window just a little on the side of the
vehicle that's away from the wind. This will help
keep CO out.
Run your engine only as long as you must. This saves
fuel. When you run the engine, make it go a little faster
than just idle. That is, push the accelerator slightly.
This uses less fuel for the heat that you get and it
keeps the battery (or batteries) charged. You will need a
well
-charged battery (or batteries) to restart the vehicle,
and possibly for signaling later on with your headlamps.
Let the heater run for a while.If you have a diesel engine, you may have to run it at a
higher speed to get enough heat. Then, shut the engine
off and close the window almost all the way to preserve
the heat. Start the engine again and repeat this only
when you feel really uncomfortable from the cold.
But do it as little as possible. Preserve the fuel as long
as you can. To help keep warm, you can get out of
the vehicle and do some fairly vigorous exercises every
half hour or so until help comes.
Recreational Vehicle Towing
Recreational vehicle towing means towing your vehicle
behind another vehicle
-- such as behind a motorhome.
The two most common types of recreational vehicle
towing are known as ªdinghy towingº (towing your
vehicle with all four wheels on the ground) and ªdolly
towingº (towing your vehicle with two wheels on
the ground and two wheels up on a device known
as a ªdollyº).
Your vehicle was not designed to be towed with any of
its wheels on the ground. If your vehicle must be towed,
see ªTowing Your Vehicleº in the Index.

4-31 If You Do Decide To Pull A Trailer
If you do, here are some important points:

There are many different laws, including speed limit
restrictions, having to do with trailering. Make sure
your rig will be legal, not only where you live but
also where you'll be driving. A good source for this
information can be state or provincial police.

Don't tow a trailer at all during the first 500 miles
(800 km) your new vehicle is driven. Your engine,
axle or other parts could be damaged.

Then, during the first 500 miles (800 km) that you
tow a trailer, don't drive over 50 mph (80 km/h) and
don't make starts at full throttle. This helps your
engine and other parts of your vehicle wear in at the
heavier loads.

If you have an automatic transmission, you can tow
in OVERDRIVE (
). You may want to shift the
transmission to THIRD (3) or, if necessary, a lower
gear selection if the transmission shifts too often
(e.g., under heavy loads and/or hilly conditions).
If you have a manual transmission and you are
towing a trailer, it's better not to use the highest gear.Three important considerations have to do with weight:

the weight of the trailer,

the weight of the trailer tongue

and the weight on your vehicle's tires.
Weight of the Trailer
How heavy can a trailer safely be?
It depends on how you plan to use your rig.
For example, speed, altitude, road grades, outside
temperature and how much your vehicle is used to
pull a trailer are all important. And, it can also depend
on any special equipment that you have on your vehicle.
Use the following chart to determine how much your
vehicle and trailer can weigh, based upon your vehicle
model and options.
3500HD models are incomplete vehicles and trailer
ratings are not assigned. Use the Gross Combination
Weight Rating (GCWR) chart to determine the
combination weight limit.

4-32
Maximum trailer weight is calculated by subtracting
the weight of your completed vehicle from the GCWR.
The weight of the completed vehicle, passengers, cargo
in the tow vehicle and the loaded trailer weight must not
exceed the GCWR.
Refer to the Trailering Guide for oil cooler
recommendations.
EngineAxle
RatioGross Combination
Weight Rating
6.5L Diesel 4.63 17,000 lbs. (7 718 kg)
5.13 17,000 lbs. (7 718 kg)
8.1L 4.63 19,000 lbs. (8 626 kg)
5.13 19,000 lbs. (8 626 kg)
You can ask your dealer for our trailering information or
advice, or you can write us at the address listed in your
Warranty and Owner Assistance Information Booklet.
In Canada, write to:
General Motors of Canada Limited
Customer Communication Centre, 163
-005
1908 Colonel Sam Drive
Oshawa, Ontario L1H 8P7
Weight of the Trailer Tongue
The tongue load (A) of any trailer is an important
weight to measure because it affects the total or gross
weight of your vehicle. The Gross Vehicle Weight
(GVW) includes the curb weight of the vehicle, any
cargo you may carry in it, and the people who will be
riding in the vehicle. And if you will tow a trailer, you
must add the tongue load to the GVW because your
vehicle will be carrying that weight, too. See ªLoading
Your Vehicleº in the Index for more information about
your vehicle's maximum load capacity.

4-36 Driving On Grades
Reduce speed and shift to a lower gear before you start
down a long or steep downgrade. If you don't shift
down, you might have to use your brakes so much
that they would get hot and no longer work well.
If you have an automatic transmission, you can tow in
AUTOMATIC OVERDRIVE (
). You may want to
shift the transmission to THIRD (3) or, if necessary, a
lower gear selection if the transmission shifts too often
(e.g., under heavy loads and/or hilly conditions).
If you have a manual transmission and you are towing a
trailer, it's better not to use FIFTH (5) gear. Just drive
in FOURTH (4) gear (or, as you need to, a lower gear).
When towing at high altitude on steep uphill grades,
consider the following: Engine coolant will boil at a
lower temperature than at normal altitudes. If you
turn your engine off immediately after towing at high
altitude on steep uphill grades, your vehicle may show
signs similar to engine overheating. To avoid this,
let the engine run while parked (preferably on level
ground) with the automatic transmission in PARK (P)
(or the manual transmission out of gear and the
parking brake applied) for a few minutes before
turning the engine off. If you do get the overheat
warning, see ªEngine Overheatingº in the Index.
Parking on Hills
CAUTION:
You really should not park your vehicle, with
a trailer attached, on a hill. If something goes
wrong, your rig could start to move. People can
be injured, and both your vehicle and the trailer
can be damaged.
But if you ever have to park your rig on a hill, here's how
to do it:
1. Apply your regular brakes, but don't shift into
PARK (P) yet for an automatic transmission,
or into gear for a manual transmission.
2. Have someone place chocks under the trailer wheels.
3. When the wheel chocks are in place, release the
regular brakes until the chocks absorb the load.
4. Reapply the regular brakes. Then apply your
parking brake and shift into PARK (P) for an
automatic transmission, or REVERSE (R) for a
manual transmission.
5. Release the regular brakes.

4-37 When You Are Ready to Leave After
Parking on a Hill
1. Apply your regular brakes and hold the pedal down
while you:

start your engine,

shift into a gear, and

release the parking brake.
2. Let up on the brake pedal.
3. Drive slowly until the trailer is clear of the chocks.
4. Stop and have someone pick up and store the chocks.
Maintenance When Trailer Towing
Your vehicle will need service more often when you're
pulling a trailer. See the Maintenance Schedule for
more on this. Things that are especially important
in trailer operation are automatic transmission fluid
(don't overfill), engine oil, axle lubricant, belts, cooling
system and brake system. Each of these is covered in
this manual, and the Index will help you find them
quickly. If you're trailering, it's a good idea to review
these sections before you start your trip.
Check periodically to see that all hitch nuts and bolts
are tight.
Trailer Wiring Harness
Power Winches
If you wish to use a power winch on your vehicle,
only use it when your vehicle is stationary or anchored.
NOTICE:
Using a power winch with the transmission in gear
may damage the transmission. When operating
a power winch, always leave the transmission
in NEUTRAL (N).
Use the regular brakes, set the parking brake, or block
the wheels to keep your vehicle from rolling.

4-38 Power Take-Off (PTO) Engine Speed
Control (If Equipped)
NOTICE:
If you have a PTO that will exceed 35 hp
installed on your vehicle, it could damage the
transmission. When having a PTO installed
on your vehicle, make sure that it will not
exceed 35 hp.
Before using a PTO, refer to the manufacturer's or
installer's instructions.
NOTICE:
Using a PTO while operating in one place
before the vehicle has reached normal operating
temperature can damage the transmission.
If you will be using the PTO while operating in
one place, drive and warm up the vehicle before
using the PTO.
To engage PTO for stationary applications
(manual transmission):
1. Hold the clutch pedal down.
2. Set the parking brake.
3. Shift the transmission into NEUTRAL.
4. Engage the PTO. Refer to the manufacturer's or
installer's instructions on electrically engaged PTOs.
5. For mobile operations, shift the transmission into the
gear you want, apply the regular brakes and release
the parking brake. For stationary operations, leave
the parking brake applied.
6. Release the clutch and regular brakes as you
normally would. When the clutch is released,
the PTO will start.
7. Turn the PTO rotary switch to ON.

4-39
NOTICE:
Using a PTO for more than four hours without
driving your vehicle can damage the transmission.
If using a PTO for more than four hours without
driving your vehicle, drive your vehicle for a while
to allow the transmission to cool.
Preset Mode: PTO speed control mode is used for
stationary applications. This mode provides a default
standby speed of 850 rpm (800 rpm with automatic
transmission) and two default PTO operation speeds
which follow:
1. PTO Set Speed of 1250 rpm, or
2. PTO Resume Speed of 1700 rpm.
The standby speed (800/850 rpm) is not to be used
as a PTO control speed. Vehicles not equipped with
cruise control will not have the resume speed capability.Using PTO speed control in Preset Mode
(Factory Setting):
1. Engage the PTO.
2. Select PARK (P) or NEUTRAL (N) range.
Apply the parking brake if NEUTRAL (N)
is selected.
3. Make sure your foot is off the brake pedal
(and off the clutch on vehicles equipped with
a manual transmission). Select the desired
engine speed for PTO operation. Be sure to
read the following Preset Mode information
regarding operation.
To engage PTO for mobile applications
(manual transmission):
If you are going to drive the vehicle, shift the
transmission into the gear you want, apply the
regular brakes and release the parking brake.
Release the clutch (and the regular brakes) as you
normally would. When you release the clutch,
the PTO will start.

4-40
To engage a PTO while the vehicle is moving:
1. Hold the clutch pedal down.
2. Shift the transmission into NEUTRAL.
3. Engage the PTO.
4. Shift the transmission into the gear you want.
5. Release the clutch as you normally would.
When you release the clutch, the PTO will start.
Variable Mode: PTO speed control mode can be used
for both stationary and mobile applications. This mode
allows PTO to be controlled in a fashion similar to how
cruise control sets vehicle speed. The operator can set an
rpm (between 800 and 2200) with the cruise control
feature or with the SET position on the PTO switch.
The operator is then able to increase rpm in increments
of 100, or ªtap,º with the resume position on the
cruise control. Or, the operator can decrease rpm in
increments of 100 with either of the SET switches on
the PTO or the cruise control. Vehicles not equipped
with cruise control will not be able to increase in
100 rpm increments.Using PTO speed control in Variable Mode:
1. Engage the PTO.
2. Make sure your foot is off the brake pedal
(and off the clutch for vehicles equipped with
a manual transmission).
3. Select the desired engine speed (with the foot pedal)
and select SET on the PTO switch or with the
cruise control.
Engine speed will be governed to the PTO maximum
engine speed (2,200 rpm) while in either the preset or
variable PTO modes. All engine speed values listed
above are factory preset values. With the exception of
the ªtapº increment (100 rpm), all of these values are
programmable and can be adjusted by your GM dealer
or body upfitter. If the PTO software settings do not
match the settings shown here, then they may have
already been altered in order to satisfy the requirements
of the installed PTO system and body equipment.

5-
5-1
Section 5 Problems on the Road
Here you'll find what to do about some problems that can occur on the road.
5
-2 Hazard Warning Flashers
5
-2 Other Warning Devices
5
-3 Jump Starting
5
-9 Towing Your Vehicle
5
-9 Engine Overheating (Gasoline Engine)5
-13 Cooling System (Gasoline Engine)
5
-21 Engine Fan Noise
5
-21 If a Tire Goes Flat
5
-22 Changing a Flat Tire
5
-23 If You're Stuck: In Sand, Mud, Ice or Snow