engine CHEVROLET C3500 HD 2001 4.G Service Manual

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.

4-32 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 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).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 can weigh, based upon your vehicle model
and options.
Maximum trailer weight is calculated assuming the
driver and one passenger are in the tow vehicle and it
has all the required trailering equipment. The weight
of additional optional equipment, passengers, cargo in
the tow vehicle and the loaded trailer weight must not
exceed the Gross Combination Weight Rating (GCWR).
Refer to the Trailering Guide for oil
cooler recommendations.

4-33
3500HD
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)
*Fifth wheel hitch rating; weight distributing hitch
rating is limited to 10,000 lbs. (4 540 kg).
3500HD models are incomplete vehicles and trailer
ratings are not assigned. Use the GCWR chart to
determine the combination weight limit.
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.

4-37
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.

4-38 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 inthis 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.
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.

4-39
Power Take-Off (PTO)
(Manual Transmission) (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 a PTO on a vehicle with a
manual transmission:
1. Hold the clutch pedal down.
2. Set the parking brake.
3. Shift the transmission into NEUTRAL (N).
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.
To engage a PTO on a vehicle with an
automatic transmission:
1. Engine speed must be less than 1000 rpm.
2. Turn the PTO rotary switch ON.

4-40
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. Torque Converter Clutch (TCC) is not
available in NEUTRAL (N) and is available only
in PARK when speed is above 1100 rpm.
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. Please read the following
Preset Mode information regarding operation.
Preset Mode: PTO speed control mode is used for
stationary applications. This mode provides a default
standby speed of 800 or 850 rpm (depending on the
engine/transmission combination) and two default
PTO control speeds which follow:
1. PTO Fast Idle Speed of 1250 rpm, or
2. PTO Fast Idle Resume Speed of 1700 rpm.
Please note that 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.
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.
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.
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.

4-41
Using PTO speed control in Variable Mode (Mobile):
1. Engage the PTO.
2. Vehicle speed must be greater than 5 mph for vehicles
equipped with gasoline engines or greater than 0 mph
for vehicles equipped with diesel engines.
3. Make sure your foot is off the brake pedal
(and off the clutch for vehicles equipped with a
manual transmission).
4. Select the desired engine speed (with the foot pedal)
and select SET on the PTO switch or with the
cruise control.
Using PTO speed control in Variable
Mode (Stationary):
1. Engage the PTO.
2. Vehicle speed must be less than 5 mph for vehicles
equipped with gasoline engines or at 0 mph for
vehicles equipped with diesel engines.
3. Make sure your foot is off the brake pedal
(and off the clutch for vehicles equipped with a
manual transmission).
4. Select the desired engine speed (with the foot pedal)
and select SET on the PTO switch or with the
cruise control.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 to
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 ªtapº, 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.
All engine speed values listed above are factory preset
values. With the exception of the TCC lockup speed
(1100 rpm) and 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
-8 Towing Your Vehicle
5
-8 Engine Overheating (Gasoline Engine)5
-11 Cooling System (Gasoline Engine)
5
-19 Engine Fan Noise
5
-19 If a Tire Goes Flat
5
-20 Changing a Flat Tire
5
-21 If You're Stuck: In Sand, Mud, Ice or Snow

5-4
1. Check the other vehicle. It must have a 12-volt
battery with a negative ground system.
NOTICE:
If the other system isn't a 12-volt system with a
negative ground, both vehicles can be damaged.
2. Get the vehicles close enough so the jumper cables
can reach, but be sure the vehicles aren't touching
each other. If they are, it could cause a ground
connection you don't want. You wouldn't be able
to start your vehicle, and the bad grounding could
damage the electrical systems.
3. To avoid the possibility of the vehicles rolling, set
the parking brake firmly on both vehicles involved
in the jump start procedure. Put an automatic
transmission in PARK (P) or a manual transmission
in NEUTRAL.
4. Turn off the ignition on both vehicles. Unplug
unnecessary accessories plugged into the cigarette
lighter or accessory power outlets. Turn off all lamps
that aren't needed as well as radios. This will avoid
sparks and help save both batteries. In addition, it
could save your radio!
NOTICE:
If you leave your radio on, it could be badly
damaged. The repairs wouldn't be covered by
your warranty.
5. Open the hoods and locate the batteries. Find the
positive (+) and negative (
-) terminals on
each battery.
CAUTION:
If your vehicle has air conditioning, the auxiliary
electric fan under the hood can start up even
when the engine is not running and can injure
you. Keep hands, clothing and tools away from
any underhood electric fan.