brakes GMC SIERRA 1999 Owner's Guide

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4-47
If your slide-in camper and its load weighs less than the
CWR, the center of gravity zone for your vehicle may
be larger.
Your dealer can help you make a good vehicle
-camper
match. He'll also help you determine your CWR.
After you've loaded your vehicle and camper, drive to a
weigh station and weigh the front and rear wheels
separately. This will tell you the loads on your axles.
The loads on the front and rear axles shouldn't be more
than either of the GAWRs. The total of the axle loads
should not be more than the GVWR.
Open your driver's door and look at the Certification/Tire
label to find out your GAWR and GVWR.
If you've gone over your weight ratings, move or take
out some things until all the weight falls below the
ratings. Of course, you should always tie down any
loose items when you load your vehicle or camper.
When you install and load your slide
-in camper, check
the manufacturer's instructions.
If you want more information on curb weights, cargo
weights, Cargo Weight Rating and the correct center of
gravity zone for your vehicle, your dealer can help you.
Just ask for a copy of ªConsumer Information,
Truck
-Camper Loading.º
Trailer Recommendations
You must subtract your hitch loads from the CWR for
your vehicle. Weigh your vehicle with the trailer attached,
so that you won't go over the GVWR or GAWR.
You'll get the best performance if you spread out the
weight of your load the right way, and if you choose the
correct hitch and trailer brakes.
For more information, see ªTrailer Towingº in
the Index.

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Towing a Trailer
CAUTION:
If you don't use the correct equipment and drive
properly, you can lose control when you pull a
trailer. For example, if the trailer is too heavy, the
brakes may not work well
-- or even at all. You
and your passengers could be seriously injured.
Pull a trailer only if you have followed all the
steps in this section. Ask your dealer for advice
and information about towing a trailer with
your vehicle.
NOTICE:
Pulling a trailer improperly can damage your
vehicle and result in costly repairs not covered by
your warranty. To pull a trailer correctly, follow
the advice in this part, and see your dealer for
important information about towing a trailer
with your vehicle.
Your vehicle may be able to tow a trailer. To identify
what the vehicle trailering capacity is for your vehicle,
you should read the information in ªWeight of the
Trailerº that appears later in this section.
If yours was built with trailering options, as many are,
it's ready for heavier trailers. But trailering is different
than just driving your vehicle by itself. Trailering means
changes in handling, durability and fuel economy.
Successful, safe trailering takes correct equipment, and
it has to be used properly.
That's the reason for this part. In it are many
time
-tested, important trailering tips and safety rules.
Many of these are important for your safety and that of
your passengers. So please read this section carefully
before you pull a trailer.

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4-56 Safety Chains
You should always attach chains between your vehicle and
your trailer. Cross the safety chains under the tongue of the
trailer to help prevent the tongue from contacting the road
if it becomes separated from the hitch. Instructions about
safety chains may be provided by the hitch manufacturer
or by the trailer manufacturer. Follow the manufacturer's
recommendation for attaching safety chains and do not
attach them to the bumper. Always leave just enough slack
so you can turn with your rig. Never allow safety chains to
drag on the ground.
Trailer Brakes
If your trailer weighs more than 1,000 lbs. (450 kg)
loaded, then it needs its own brakes
-- and they must be
adequate. Be sure to read and follow the instructions for
the trailer brakes so you'll be able to install, adjust and
maintain them properly.
Your trailer brake system can tap into the vehicle's
hydraulic brake system only if:

The trailer parts can withstand 3,000 psi
(20 650 kPa) of pressure.
The trailer's brake system will use less than
0.02 cubic inch (0.3 cc) of fluid from your vehicle's
master cylinder. Otherwise, both braking systems
won't work well. You could even lose your brakes.
If everything checks out this far, make the brake tap at the
port on the master cylinder that sends the fluid to the rear
brakes. But don't use copper tubing for this. If you do, it
will bend and finally break off. Use steel brake tubing.
Driving with a Trailer
Towing a trailer requires a certain amount of experience.
Before setting out for the open road, you'll want to get
to know your rig. Acquaint yourself with the feel of
handling and braking with the added weight of the
trailer. And always keep in mind that the vehicle you are
driving is now a good deal longer and not nearly as
responsive as your vehicle is by itself.
Before you start, check the trailer hitch and platform
(and attachments), safety chains, electrical connector,
lamps, tires and mirror adjustment. If the trailer has
electric brakes, start your vehicle and trailer moving and
then apply the trailer brake controller by hand to be sure
the brakes are working. This lets you check your
electrical connection at the same time.

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4-57
During your trip, check occasionally to be sure that the
load is secure, and that the lamps and any trailer brakes
are still working.
Following Distance
Stay at least twice as far behind the vehicle ahead as you
would when driving your vehicle without a trailer. This
can help you avoid situations that require heavy braking
and sudden turns.
Passing
You'll need more passing distance up ahead when
you're towing a trailer. And, because you're a good deal
longer, you'll need to go much farther beyond the
passed vehicle before you can return to your lane.
Backing Up
Hold the bottom of the steering wheel with one hand.
Then, to move the trailer to the left, just move that hand
to the left. To move the trailer to the right, move your
hand to the right. Always back up slowly and, if
possible, have someone guide you.
Making Turns
NOTICE:
Making very sharp turns while trailering could
cause the trailer to come in contact with the
vehicle. Your vehicle could be damaged. Avoid
making very sharp turns while trailering.
When you're turning with a trailer, make wider turns than
normal. Do this so your trailer won't strike soft shoulders,
curbs, road signs, trees or other objects. Avoid jerky or
sudden maneuvers. Signal well in advance.
Turn Signals When Towing a Trailer
The arrows on your instrument panel will flash
whenever you signal a turn or lane change. Properly
hooked up, the trailer lamps will also flash, telling other
drivers you're about to turn, change lanes or stop.
When towing a trailer, the arrows on your instrument
panel will flash for turns even if the bulbs on the trailer
are burned out. Thus, you may think drivers behind you
are seeing your signal when they are not. It's important
to check occasionally to be sure the trailer bulbs are
still working.

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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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4-61 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.
Power Take-Off (PTO)
(Manual Transmission)
NOTICE:
If you have a PTO that will exceed 35 hp installed
on your vehicle, it could damage the transfer case
or 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 transfer case or
transmission. If you will be using the PTO while
operating in one place, drive and warm up the
vehicle before using the PTO.

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To engage a PTO:
1. Hold the clutch pedal down.
2. Set the parking brake.
3. Shift the transmission into NEUTRAL (N).
4. Engage the PTO.
NOTICE:
Using a PTO for more than four hours without
driving your vehicle can damage the transfer case
or transmission. If using a PTO for more than
four hours without driving your vehicle, drive
your vehicle for a while to allow the transfer case
and transmission to cool.
If you are going to drive the vehicle, shift the
transfer case into the range you want (if you have
four
-wheel drive). Then shift the transmission into
the gear you want, apply the regular brakes and
release the parking brake.
5. 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 (N).
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.
Using a Transfer Case Mounted Power
Take-Off (Manual Transmission)
1. Hold the clutch pedal down.
2. Set the parking brake.
3. Shift the transfer case into NEUTRAL (N).
4. If the vehicle will remain in the same place, shift the
transmission into the highest gear.
5. Engage the PTO.
If you are going to drive the vehicle, shift the
transmission into the gear you want. Then shift the
transfer case into the range you want, apply the
regular brakes and release the parking brake.
6. Release the clutch (and the regular brakes) as you
normally would. When you release the clutch, the
PTO will start.

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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.

6-
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Section 6 Service and Appearance Care
Here you will find information about the care of your vehicle. This section begins with service and fuel information,
and then it shows how to check important fluid and lubricant levels. There is also technical information about your
vehicle, and a part devoted to its appearance care.
6
-2 Service
6
-3 Fuel (Gasoline Engine)
6
-5 Fuels in Foreign Countries (Gasoline Engines)
6
-5 Filling Your Tank (Gasoline Engine)
6
-8 Filling a Portable Fuel Container
6
-8 Checking Things Under the Hood
6
-12 Noise Control System
6
-13 Engine Oil (Gasoline Engine)
6
-17 Engine Air Cleaner/Filter (Gasoline Engines)
6
-20 Automatic Transmission Fluid
6
-23 Manual Transmission Fluid
6
-24 Hydraulic Clutch
6
-25 Rear Axle
6
-26 Four-Wheel Drive
6
-27 Radiator Pressure Cap (Gasoline Engine)
6
-28 Thermostat
6
-28 Engine Coolant6
-32 Power Steering Fluid
6
-33 Windshield Washer Fluid
6
-34 Brakes
6
-38 Battery
6
-39 Bulb Replacement
6
-49 Windshield Wiper Blade Replacement
6
-50 Tires
6
-61 Appearance Care
6
-61 Cleaning the Inside of Your Vehicle
6
-65 Cleaning the Outside of Your Vehicle
6
-68 GM Vehicle Care/Appearance Materials
6
-69 Vehicle Identification Number (VIN)
6
-69 Electrical System
6
-75 Replacement Bulbs
6
-76 Capacities and Specifications
6
-78 Air Conditioning Refrigerants
6
-78 Normal Maintenance Replacement Parts