GMC SIERRA 1999 Owner's Manual

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4-49
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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4-50 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.

Consider using a sway control if your trailer will
weigh less than the capacity stamped on your step
bumper. You should always use a sway control if
your trailer will weigh more than the capacity
stamped on your step bumper. You can ask a hitch
dealer about sway controls.

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 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.

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Use one of the following charts 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 and cargo in
the tow vehicle must be subtracted from the maximum
trailer weight.
Above the 2,000 lbs. (908 kg) trailer rating, the engine
oil cooler is required on C/K
-2500 models with gas
engines. Refer to the Trailering Guide for oil cooler
recommendations.C
-1500 (2WD)
Engine (Trans.) Axle Ratio Max. Trailer Wt.
5.0L 3.08 4,500 lbs. (2 043 kg)
3.42 5,500 lbs. (2 497 kg)
3.73 6,500 lbs. (2 951 kg)
5.7L 3.08 5,000 lbs. (2 270 kg)
3.42 6,000 lbs. (2 724 kg)
3.73 7,000 lbs. (3 178 kg)
K
-1500 (4WD)
Engine (Trans.) Axle Ratio Max. Trailer Wt.
5.0L 3.42 5,000 lbs. (2 270 kg)
3.73 6,000 lbs. (2 724 kg)
5.7L 3.42 5,500 lbs. (2 497 kg)
3.73 6,500 lbs. (2 951 kg)
6.5L Diesel 3.42 6,000 lbs. (2 724 kg)
3.73 7,000 lbs. (3 178 kg)

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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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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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If you're using a weight-carrying hitch, the trailer
tongue (A) should weigh 10 percent of the total loaded
trailer weight (B). If you're using a weight
-distributing
hitch, the trailer tongue (A) should weigh 12 percent of
the total loaded trailer weight (B).
After you've loaded your trailer, weigh the trailer and
then the tongue, separately, to see if the weights are
proper. If they aren't, you may be able to get them right
simply by moving some items around in the trailer.
Total Weight on Your Vehicle's Tires
Be sure your vehicle's tires are inflated to the upper
limit for cold tires. You'll find these numbers on the
Certification label at the rear edge of the driver's door or
see ªTire Loadingº in the Index. Then be sure you don't
go over the GVW limit for your vehicle, including the
weight of the trailer tongue.
Hitches
It's important to have the correct hitch equipment.
Crosswinds, large trucks going by and rough roads are
a few reasons why you'll need the right hitch. Here are
some rules to follow:

If you use a step
-bumper hitch, your bumper could
be damaged in sharp turns. Make sure you have
ample room when turning to avoid contact between
the trailer and the bumper.

If you'll be pulling a trailer that, when loaded, will
weigh more than the capacity stamped on your step
bumper, be sure to use a properly mounted,
weight
-distributing hitch and sway control of the
proper size. This equipment is very important for
proper vehicle loading and good handling when
you're driving.

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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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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.