2009 HUMMER H3 trailer

Maximum trailer weight is calculated
assuming only the driver is in the
tow vehicle and it has all the
required trailering equipment. Theweight of additional optional
equipment, passengers and cargo in
the tow vehicle must be subtracted
from the maximum trailer weight.Use the following chart to determine
how much the vehicle can weigh,
based upon the vehicle model
and options.
Vehicle
Axle Ratio Maximum Trailer Weight *GCWR
H3 3.7L L5 Engine, Automatic
Transmission 4.56
4,500 lbs (2 041 kg) 9,500 lbs (4 309 kg)
3.7L L5 Engine, Manual
Transmission 4.56
3,000 lbs (1 361 kg) 8,000 lbs (3 629 kg)
5.3L V8 Engine, Automatic
Transmission 4.10
6,000 lbs (2 721 kg) 11,400 lbs (5 171 kg)
H3T 3.7L L5 Engine, Automatic
Transmission 4.56
4,400 lbs (1 996 kg) 9,500 lbs (4 309 kg)
3.7L L5 Engine, Manual
Transmission 4.56
2,900 lbs (1 315 kg) 8,000 lbs (3 629 kg)
5.3L V8 Engine, Automatic
Transmission 4.10
5,900 lbs (2 676 kg) 11,400 lbs (5 171 kg)
*The Gross Combination Weight Rating (GCWR) in the total allowable weight of the completely loaded vehicle and
trailer including any passengers, cargo, equipment and conversions. The GCWR for the vehicle should not be
exceeded.
Ask your dealer/retailer for our
trailering information or advice, or
write us at our Customer Assistance Offices. See
Customer Assistance
Offices on page 7-4 for more
information.
4-44 Driving Your Vehicle

Weight of the Trailer Tongue
The tongue load (A) of any trailer is
an important weight to measure
because it affects the total gross
weight of the vehicle. The Gross
Vehicle Weight (GVW) includes the
curb weight of the vehicle, any
cargo carried in it, and the people
who will be riding in the vehicle.If
there are a lot of options, equipment,
passengers or cargo in the vehicle,
it will reduce the tongue weight
the vehicle can carry, which will also
reduce the trailer weight the
vehicle can tow. If towing a trailer,
the tongue load must be added
to the GVW because the vehicle will
be carrying that weight, too. See
Loading the Vehicle on page 4-35
for more information about the
vehicle’s maximum load capacity.The trailer tongue weight (A) should
be 10 percent to 15 percent of
the total loaded trailer weight (B), up
to a maximum of 500 lbs (227 kg)
with a weight carrying hitch or
a weight distributing hitch.
Do not exceed the maximum
allowable tongue weight for the
vehicle. Choose the shortest hitch
extension that will position the
hitch ball closest to the vehicle.
This will help reduce the effect of
trailer tongue weight on the
rear axle.If the spare tire carrier is mounted
on the back of the vehicle and
the hitch extension is too short,
the spare tire may interfere
with trailer coupling or trailer tongue
jack operation on some types of
trailers.
After loading the trailer, weigh the
trailer and then the tongue,
separately, to see if the weights are
proper. If they aren’t, adjustments
might be made by moving some
items around in the trailer.
Driving Your Vehicle 4-45

Total Weight on the Vehicle’s
Tires
Be sure the vehicle’s tires are
inated to the upper limit for cold
tires. These numbers can be found
on the Certication/Tire Label
located on the B-pillar below the
door latch or seeLoading the
Vehicle on page 4-35. Make sure
not to go over the GVW limit for the
vehicle, or the GAWR, including
the weight of the trailer tongue. If
using a weight distributing hitch,
make sure not to go over the rear
axle limit before applying the weight
distribution spring bars.
Hitches
It is important to have the correct
hitch equipment. Crosswinds,
large trucks going by and rough
roads are a few reasons why
the right hitch is needed.Weight-Distributing Hitches and
Weight Carrying Hitches
When using a weight-distributing
hitch, the hitch must be adjusted so
that the distance (A) remains the
same both before and after coupling
the trailer to the tow vehicle.
Trailering may also be limited by the
vehicle’s ability to carry tongue
weight. Tongue weight cannot cause
the vehicle to exceed the GVWR(Gross Vehicle Weight Rating) or
the RGAWR (Rear Gross Axle
Weight Rating). The effect of
additional weight can reduce the
trailering capacity more than
the total of the additional weight.
Consider the following example:
A vehicle model base weight
is 5,500 lbs (2 495 kg); 2,800 lbs
(1 270 kg) at the front axle and
2,700 lbs (1 225 kg) at the rear axle.
It has a GVWR of 7,200 lbs
(3 266 kg), a RGAWR of 4,000 lbs
(1 814 kg) and a GCWR (Gross
Combination Weight Rating)
of 14,000 lbs (6 350 kg). The trailer
rating should be:
Expect tongue weight to be at least
10 percent of trailer weight
(850 lbs (386 kg)) and because the
weight is applied well behind the (A) Body-to-Ground Distance (B)
Front of Vehicle
4-46 Driving Your Vehicle

rear axle, the effect on the
rear axle is greater than just the
weight itself, as much as 1.5 times
as much. The weight at the rear
axle could be 850 lbs (386 kg)
X 1.5 = 1,275 lbs (578 kg). Since
the rear axle already weighs
2,700 lbs (1 225 kg), adding
1,275 lbs (578 kg) brings the total to
3,975 lbs (1 803 kg). This is very
close to, but within the limit for
RGAWR as well. The vehicle is set
to trailer up to 8,500 lbs (3 856 kg).If the vehicle has many options and
there is a front seat passenger
and two rear seat passengers with
some luggage and gear in the
vehicle as well, 300 lbs (136 kg)
could be added to the front
axle weight and 400 lbs (181 kg) to
the rear axle weight. The vehicle
now weighs:
Weight is still below 7,200 lbs
(3 266 kg) and you might think
700 additional pounds (318 kg)
should be subtracted from the
trailering capacity to stay within
GCWR limits. The maximum trailer
would only be 7,800 lbs (3 538 kg).
You may go further and think
the tongue weight should be limitedto less than 1,000 lbs (454 kg) to
avoid exceeding GVWR. But
the effect on the rear axle must still
be considered. Because the rear
axle now weighs 3,100 lbs
(1 406 kg), 900 lbs (408 kg) can be
put on the rear axle without
exceeding RGAWR. The effect of
tongue weight is about 1.5 times the
actual weight. Dividing the 900 lbs
(408 kg) by 1.5 leaves only
600 lbs (272 kg) of tongue weight
that can be handled. Since
tongue weight is usually at least
10 percent of total loaded trailer
weight, expect that the largest trailer
the vehicle can properly handle is
6,000 lbs (2 721 kg).
It is important that the vehicle
does not exceed any of its
ratings — GCWR, GVWR, RGAWR,
Maximum Trailer Rating or
Tongue Weight. The only way
to be sure it is not exceeding any of
these ratings is to weigh the vehicle
and trailer.
Driving Your Vehicle 4-47

Safety Chains
Always attach chains between the
vehicle and the 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. Always leave just enough
slack so the rig can turn. Never
allow safety chains to drag on the
ground.
Trailer Brakes
A loaded trailer that weighs more
than 1,500 lbs (680 kg) needs
to have its own brake system that is
adequate for the weight of the
trailer. Be sure to read and follow
the instructions for the trailer brakes
so they are installed, adjusted
and maintained properly.
Driving with a Trailer
Towing a trailer requires a certain
amount of experience. Get to
know the rig before setting out for
the open road. Get acquainted
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
longer and not as responsive as the
vehicle is by itself.
Before starting, check all trailer hitch
parts and attachments, safety
chains, electrical connectors, lamps,
tires and mirror adjustments. If
the trailer has electric brakes, start
the vehicle and trailer moving
and then apply the trailer brake
controller by hand to be sure
the brakes are working. This checks
the electrical connection at the
same time.
During the 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 the vehicle without a
trailer. This can help to avoid
situations that require heavy braking
and sudden turns.
Passing
More passing distance is needed
when towing a trailer. Because
the rig is longer, it is necessary to
go much farther beyond the
passed vehicle before returning to
the lane.
Backing Up
Hold the bottom of the steering
wheel with one hand. Then, to move
the trailer to the left, 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.
4-48 Driving Your Vehicle

Making Turns
Notice:Making very sharp turns
while trailering could cause
the trailer to come in contact with
the vehicle. The vehicle could
be damaged. Avoid making very
sharp turns while trailering.
When turning with a trailer, make
wider turns than normal. Do this
so the 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 the instrument panel
ash whenever signaling a turn
or lane change. Properly hooked up,
the trailer lamps also ash, telling
other drivers the vehicle is turning,
changing lanes or stopping.When towing a trailer, the arrows
on the instrument panel ash
for turns even if the bulbs on the
trailer are burned out. For this
reason you may think other drivers
are seeing the signal when they
are not. It is important to check
occasionally to be sure the trailer
bulbs are still working.
Driving On Grades
Reduce speed and shift to a lower
gearbeforestarting down a long
or steep downgrade. If the
transmission is not shifted down, the
brakes might have to be used so
much that they would get hot and no
longer work well.
Vehicles with an automatic
transmission can tow in D (Drive).
Shift the transmission to a lower
gear if the transmission shifts
too often under heavy loads and/or
hilly conditions. For vehicles with
a manual transmission, it is
better not to use the highest 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 the engine is
turned off immediately after towing
at high altitude on steep uphill
grades, the 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 P (Park) for a
few minutes before turning the
engine off. For vehicles with manual
transmissions, let the engine run
while parked, preferably on
level ground, with the transmission
out of gear and the parking
brake applied, for a few minutes
before turning the engine off. If the
overheat warning comes on,
seeEngine Overheating on
page 5-27.
Driving Your Vehicle 4-49

Parking on Hills
{CAUTION
Parking the vehicle on a hill with
the trailer attached can be
dangerous. If something goes
wrong, the rig could start to move.
People can be injured, and both
the vehicle and the trailer can be
damaged. When possible, always
park the rig on a at surface.
If parking the rig on a hill:
1. Press the brake pedal, but do
not shift into P (Park) yet for
vehicles with an automatic
transmission, or into gear for
vehicles with a manual
transmission. Turn the wheels
into the curb if facing downhill or
into traffic if facing uphill.2. Have someone place chocks
under the trailer wheels.
3. When the wheel chocks are in
place, release the brake pedal
until the chocks absorb the load.
4. Reapply the brake pedal.
Then apply the parking brake and
shift into P (Park) for vehicles
with an automatic transmission or
into gear for vehicles with a
manual transmission.
5. Release the brake pedal.
Leaving After Parking on
a Hill
The vehicle has a Hill Start Assist
feature, which may be useful
when stopped on a grade. See
Braking on page 4-3for more
information.
1. Apply and hold the brake pedal
while you:
start the 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.
4-50 Driving Your Vehicle

Maintenance When Trailer
Towing
The vehicle needs service more
often when pulling a trailer. See this
manual’s Maintenance Schedule
or Index for more information.
Things that are especially important
in trailer operation are automatic
transmission uid, engine oil,
axle lubricant, belts, cooling system
and brake system. It is a good
idea to inspect these before and
during the trip.
Check periodically to see that all
hitch nuts and bolts are tight.
Trailer Wiring Harness
Light-Duty Trailer Wiring Package
If the vehicle does not have a
trailer towing package, the chassis
harness will contain the following
blunt cut circuits:
Yellow: Left Stop/Turn Signal
Dark Green: Right Stop/Turn
Signal
White: Ground
Brown: Tail Lamps
To add a trailer towing wiring
package, have it installed by your
dealer/retailer or a qualied
service center. Also, seeAdd-On
Electrical Equipment on page 5-91
for more information.Heavy-Duty Trailer Wiring
Package
If the vehicle has a trailer towing
package, the rear bumper harness
will have a seven-pin universal
heavy-duty trailer connector
attached to a bracket on the hitch
platform.
Driving Your Vehicle 4-51