engine GMC SIERRA 1999 Workshop Manual

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4-52
C-2500 (2WD)
Engine (Trans.) Axle Ratio Max. Trailer Wt.
5.7L 3.42 6,000 lbs. (2 724 kg)
3.73 7,000 lbs. (3 178 kg)
4.10 8,000 lbs. (3 632 kg)
6.5L Diesel 3.42 6,500 lbs. (2 951 kg)
3.73 7,500 lbs. (3 405 kg)
4.10 8,500 lbs. (3 859 kg)
7.4L 3.73 9,000 lbs. (4 086 kg)
4.10 11,000 lbs.* (4 994 kg)
*Fifth
-wheel hitch rating; weight-distributing hitch
rating is limited to 10,000 lbs. (4 540 kg).K
-2500 (4WD)
Engine (Trans.) Axle Ratio Max. Trailer Wt.
5.7L 3.73 6,000 lbs. (2 724 kg)
4.10 7,500 lbs. (3 405 kg)
6.5L Diesel 3.73 6,500 lbs. (2 951 kg)
4.10 8,000 lbs. (3 632 kg)
7.4L 3.73 8,500 lbs. (3 859 kg)
4.10 10,500 lbs.* (4 767 kg)
*Fifth
-wheel hitch rating; weight-distributing hitch
rating is limited to 10,000 lbs. (4 540 kg).

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4-53
C-3500 (2WD)
Engine (Trans.) Axle Ratio Max. Trailer Wt.
5.7L 4.10 7,500 lbs. (3 405 kg)
4.56 9,000 lbs. (4 086 kg)
6.5L Diesel 4.10 8,000 lbs. (3 632 kg)
7.4L 4.10 10,500 lbs.* (4 767 kg)
4.56 12,500 lbs.* (5 675 kg)
*Fifth
-wheel hitch rating; weight-distributing hitch
rating is limited to 10,000 lbs. (4 540 kg).
K
-3500 (4WD)
Engine (Trans.) Axle Ratio Max. Trailer Wt.
5.7L 4.10 7,000 lbs. (3 178 kg)
6.5L Diesel 4.10 7,500 lbs. (3 405 kg)
7.4L 4.10 10,000 lbs. (4 540 kg)
4.56 12,000 lbs.* (5 448 kg)
*Fifth
-wheel hitch rating; weight-distributing hitch
rating is limited to 10,000 lbs. (4 540 kg).C
-3500 Crew Cab (2WD)
Engine (Trans.) Axle Ratio Max. Trailer Wt.
5.7L 4.10 7,000 lbs. (3 178 kg)
4.56 8,500 lbs. (3 859 kg)
6.5L Diesel 4.10 8,000 lbs. (3 632 kg)
7.4L 4.10 10,500 lbs.* (4 767 kg)
4.56 12,500 lbs.* (5 675 kg)
*Fifth
-wheel hitch rating; weight-distributing hitch
rating is limited to 10,000 lbs. (4 540 kg).
K
-3500 Crew Cab (4WD)
Engine (Trans.) Axle Ratio Max. Trailer Wt.
5.7L 4.10 6,500 lbs. (2 951 kg)
4.56 8,000 lbs. (3 632 kg)
6.5L Diesel 4.10 7,500 lbs. (3 405 kg)
7.4L 4.10 10,000 lbs.* (4 540 kg)
4.56 12,000 lbs.* (5 448 kg)
*Fifth
-wheel hitch rating; weight-distributing hitch
rating is limited to 10,000 lbs. (4 540 kg).

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4-54
C-3500 HD Chassis Cab
Engine (Trans.) Axle Ratio Max. Trailer Wt.
6.5L Diesel
(Auto.)4.63 9,000 lbs. (4 086 kg)
5.13 10,000 lbs.* (4 540 kg)
7.4L 4.63 12,000 lbs.* (5 448 kg)
5.13 12,000 lbs.* (5 448 kg)
*Fifth
-wheel hitch rating; weight-distributing hitch
rating is limited to 10,000 lbs. (4 540 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
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.

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4-58 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.

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4-59
5. If you have a four-wheel-drive vehicle, be sure
the transfer case is in a drive gear and not in
NEUTRAL (N).
6. Release the regular brakes.
CAUTION:
It can be dangerous to get out of your vehicle if
the shift lever is not fully in PARK (P) with the
parking brake firmly 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 won't move, even
when you're on fairly level ground, use the steps
that follow.
Always put the shift lever fully in PARK (P) with
the parking brake firmly set.
If the transfer case on four-wheel drive vehicles is
in NEUTRAL (N), your vehicle will be free to
roll, even if your shift lever is in PARK (P). So, be
sure the transfer case is in a drive gear
-- not in
NEUTRAL (N).
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, belt, 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.

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4-63 Using a Transfer Case Mounted Power
Take-Off (Automatic Transmission)
1. Set the parking brake.
2. Turn the ignition off.
3. Shift the transfer case into NEUTRAL (N).
4. Shift the transmission into NEUTRAL (N).
5. Engage the PTO.
If you are going to drive the vehicle, shift the
transfer case into the range you want. Turn the
ignition to START. Then apply the regular brakes
and release the parking brake.
6. Shift the transmission to THIRD (3) to start the PTO.
7. Release the regular brakes to drive the vehicle.
Disengaging a Power Take-Off
1. Turn the ignition off.
2. Put the transmission in PARK (P).
3. Release the PTO
4. Restart the engine.
Step-Bumper Pad
If your vehicle has a rear step bumper, it may
be equipped with a rear step pad at the center of
the bumper.
If you will be using the
bumper to tow a trailer, you
must remove the center
cutout circle to install the
trailer ball. You must
also remove both outer
cutouts to attach the
trailer safety chains.
To remove the pad, lift the
edge of the pad from the
rear of the bumper and
swing it forward. When the
pad releases from the
bumper holes, lift the
pad off.

5-
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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
-3 Other Warning Devices
5
-3 Jump Starting
5
-8 Towing Your Vehicle
5
-9 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
-32 If You're Stuck: In Sand, Mud, Ice or Snow

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5-4
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.
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 (N). If you have a four
-wheel-drive
vehicle, be sure the transfer case is not in
NEUTRAL (N).
3. 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.
4. 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.

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5-5
CAUTION:
Using a match near a battery can cause battery
gas to explode. People have been hurt doing this,
and some have been blinded. Use a flashlight if
you need more light.
Be sure the batteries have enough water.
You don't need to add water to the ACDelco
Freedom

battery (or batteries) installed in
every new GM vehicle. But if a battery has filler
caps, be sure the right amount of fluid is there.
If it is low, add water to take care of that first.
If you don't, explosive gas could be present.
Battery fluid contains acid that can burn you.
Don't get it on you. If you accidentally get it in
your eyes or on your skin, flush the place with
water and get medical help immediately.
5. Check that the jumper cables don't have loose or
missing insulation. If they do, you could get a shock.
The vehicles could be damaged too.
Before you connect the cables, here are some basic
things you should know. Positive (+) will go to
positive (+) and negative (
-) will go to a heavy
unpainted metal engine part. Don't connect positive
(+) to negative (
-) or you'll get a short that would
damage the battery and maybe other parts too.
On vehicles equipped with dual batteries, make any
battery connections to the primary battery located on
the passenger's side of the vehicle.
CAUTION:
Fans or other moving engine parts can injure you
badly. Keep your hands away from moving parts
once the engine is running.

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5-7
9. Attach the cable at least 18 inches (45 cm) away
from the dead battery, but not near engine parts that
move. The electrical connection is just as good
there, but the chance of sparks getting back to the
battery is much less.
10. Now start the vehicle with the good battery and run
the engine for awhile.
11. Try to start the vehicle with the dead battery.
If it won't start after a few tries, it probably
needs service.12. Remove the cables in reverse order to prevent
electrical shorting. Take care that they don't touch
each other or any other metal.
A. Heavy Metal Engine Part
B. Good Battery
C. Dead Battery