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208 Driving and Operating
Trailer Towing
If the vehicle has a diesel engine,
see the Duramax diesel
supplement.
{Warning
The driver can lose control when
pulling a trailer if the correct
equipment is not used or the
vehicle is not driven properly. For
example, if the trailer is too heavy
or the trailer brakes are
inadequate for the load, the
vehicle may not stop as expected.
The driver and passengers could
be seriously injured. The vehicle
may also be damaged; the
resulting repairs would not be
covered by the vehicle warranty.
Pull a trailer only if all the steps in
this section have been followed.
Ask your dealer for advice and
information about towing a trailer
with the vehicle.
Caution
Pulling a trailer improperly can
damage the vehicle and result in
costly repairs not covered by the
vehicle warranty. To pull a trailer
correctly, follow the advice in this
section and see your dealer for
important information about
towing a trailer with the vehicle.
To identify the trailering capacity of
the vehicle, read the information in
“Weight of the Trailer” following.
Trailering is different than just
driving the vehicle by itself.
Trailering means changes in
handling, acceleration, braking,
durability, and fuel economy.
Successful, safe trailering takes
correct equipment, and it has to be
used properly.
The following information has 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 pulling a
trailer.
Weight of the Trailer
Safe trailering requires monitoring
the weight, speed, altitude, road
grades, outside temperature, and
how frequently the vehicle is used to
pull a trailer are all important. Take
into consideration any special
equipment on the vehicle, and the
amount of tongue weight the vehicle
can carry. See
“Weight of the Trailer
Tongue” later in this section.
Maximum trailer weight is calculated
assuming only the driver is 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.
Use the following chart to determine
how much the vehicle can weigh,
based upon the vehicle model and
options.
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VehicleAxle Ratio Maximum Trailer Weight GCWR (a)
G2500 Cargo Van 2WD Short Wheelbase 4.8L V8 3.424 037 kg (8,900 lb) 6 623 kg (14,600 lb)
6.0L V8 3.424 536 kg (10,000 lb) 7 257 kg (16,000 lb)
G2500 Cargo Van 2WD Long Wheelbase 4.8L V8 3.423 719 kg (8,200 lb) 6 623 kg (14,600 lb)
6.0L V8 3.424 536 kg (10,000 lb) 7 257 kg (16,000 lb)
G2500 Passenger Van 2WD Short Wheelbase 4.8L V8 3.423 946 kg (8,700 lb) 6 623 kg (14,600 lb)
6.0L V8 3.424 355 kg (9,600 lb) 7 257 kg (16,000 lb)
G3500 Cargo Van 2WD Short Wheelbase 4.8L V8 3.424 037 kg (8,900 lb) 6 623 kg (14,600 lb)
6.0L V8 3.424 536 kg (10,000 lb) 7 257 kg (16,000 lb)
G3500 Cargo Van 2WD Long Wheelbase
4.8L V8 3.423 946 kg (8,700 lb) 6 623 kg (14,600 lb)
6.0L V8 3.424 536 kg (10,000 lb) 7 257 kg (16,000 lb)
G3500 Passenger Van 2WD Short Wheelbase
4.8L V8 3.423 719 kg (8,200 lb) 6 623 kg (14,600 lb)
6.0L V8 3.424 355 kg (9,600 lb) 7 257 kg (16,000 lb)
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210 Driving and Operating
VehicleAxle Ratio Maximum Trailer Weight GCWR (a)
G3500 Passenger Van 2WD Long Wheelbase 4.8L V8 3.423 583 kg (7,900 lb) 6 623 kg (14,600 lb)
6.0L V8 3.424 218 kg (9,300 lb) 7 257 kg (16,000 lb)
3500 Series Cutaway –353 cm (139 in) Wheelbase
4.8L V8 3.42/3.73(b)6 623 kg (14,600 lb)
6.0L V8 3.42/3.73(b)7 257 kg (16,000 lb)
3500 Series Cutaway –404 cm (159 in) Wheelbase
4.8L V8 3.42/3.73(b)6 623 kg (14,600 lb)
6.0L V8 3.42/3.73(b)7 257 kg (16,000 lb)
6.0L V8 4.10(b)8 618 kg (19,000 lb)
6.0L V8 4.10(b)9 072 kg (20,000 lb)
3500 Series Cutaway –450 cm (177 in) Wheelbase
6.0L V8 3.42/3.73(b)7 257 kg (16,000 lb)
6.0L V8 4.10(b)8 618 kg (19,000 lb)
6.0L V8 4.10(b)9 072 kg (20,000 lb)
(a) *The Gross Combined Weight Rating (GCWR) is the total allowable weight of the completely loaded vehicle
and trailer including any passengers, cargo, equipment, and conversion. The GCWR for the vehicle should not be
exceeded.
(b) Maximum Trailer Weight cannot be provided because total vehicle weight is unknown.
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Driving and Operating 211
Ask your dealer for trailering
information or advice.
Weight of the Trailer Tongue
The tongue load (1) 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
Vehicle Load Limits0173 for more
information about the vehicle's
maximum load capacity.
The trailer tongue weight (1) should
be 10 percent to 15 percent of the
total loaded trailer weight (2), up to a
maximum of 181 kg (400 lb) with a
weight carrying hitch. The trailer
tongue weight (1) should be
10 percent to 15 percent of the total
loaded trailer weight (2), up to a
maximum of 454 kg (1,000 lb) with 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. After loading the trailer, weigh the
trailer and then the tongue,
separately, to see if the weights are
proper. If they are not, adjustments
might be made by moving some
items around in the trailer.
Trailering may 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 may reduce the
trailering capacity more than the
total of the additional weight.
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.
Total Weight on the Vehicle's
Tires
Be sure the vehicle tires are inflated
to the upper limit for cold tires.
These numbers can be found on the
Certification label at the rear edge of
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212 Driving and Operating
the driver door, or seeVehicle Load
Limits 0173. 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.
Towing Equipment
Hitches
The correct hitch equipment helps
maintain combination control. Many
trailers can be towed with a
weight-carrying hitch which simply
features a coupler latched to the
hitch ball, or a tow eye latched to a
pintle hook. Other trailers may
require a weight-distributing hitch
that uses spring bars to distribute
the trailer tongue weight among the
two vehicle and trailer axles. See
“Weight of the Trailer Tongue” under
Trailer Towing 0208 for rating limits
with various hitch types. Consider using sway controls with
any trailer. Ask a trailering
professional about sway controls or
refer to the trailer manufacturer's
recommendations and instructions.
Weight-Distributing Hitches
and Weight Carrying Hitches
A weight distributing hitch may be
useful with some trailers. Use the
following guidelines to determine if a
weight distributing hitch should
be used.
1. Front of Vehicle
2. Body to Ground Distance
When using a weight-distributing
hitch, the hitch must be adjusted so
the distance (2) remains the same
both before and after coupling the
trailer to the tow vehicle.
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 680 kg (1,500 lb) must be
equipped with its own brake system,
with brakes working on all axles.
Trailer braking equipment
conforming to Canadian Standards
Association (CSA) requirement
CAN3-D313, or its equivalent, is
recommended.
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Driving and Operating 213
State and local regulations may also
require the trailer to have its own
braking system if loaded above a
certain threshold.
Be sure to read and follow the
instructions for the trailer brakes so
they are installed, adjusted, and
maintained properly.
Do not tap into the vehicle's
hydraulic brake system.
Trailer Wiring Harness
The optional heavy-duty trailer
wiring package includes a wiring
harness, with a seven-pin connector
at the rear of the vehicle and a
four-wire harness assembly under
the driver side of the instrument
panel. The four-wire harness
assembly comes without a
connector.
If the vehicle does not have a trailer
hitch, the seven-wire harness
assembly with connector is taped
together and located in a frame
pocket at the driver side rear left
corner of the frame.If the vehicle has a trailer hitch, the
seven-wire harness assembly with
connector is attached to a bracket
on the hitch platform. In both cases,
the seven-wire harness has a
connector and includes a 30-amp
feed wire.
Use only a round, seven-wire
connector with flat blade terminals
meeting SAE J2863 specifications
for proper electrical connectivity.
The seven-wire harness connector
contains the following trailer circuits:
.
Light Green: Back-up Lamps
(10A fuse)**
. White: Ground
. Dark Blue: Trailer Brake Signal
. Dark Green: Right Rear Stop
and Turn Signal*
. Red/Black Stripe: Battery Feed
(30A Fuse)
. Brown: Trailer Park Lamp
Supply Voltage (15A fuse)**
. Yellow: Left Rear Stop and Turn
Signal * The four-wire harness (without
connector) contains the following
circuits:
.
Black: Ground
. Red/White: Battery Feed
. Dark Blue: Trailer Brake Signal
. Light Blue: CHMSL/Stoplamp
Supply Voltage
* If the vehicle is a cutaway with
trailer provisions, a 15 amp fuse will
be shared for both left/stop trailer
turn and right/stop trailer turn
signals. However, the cutaway
lighting connector will have a
10 amp fuse for each signal.
** If the vehicle is a cutaway with
trailer provisions, a 15 amp fuse will
be shared for trailer park lamps and
cutaway rear lighting connector park
lamps. Also, a 10 amp fuse will be
shared for trailer back-up lamps and
cutaway rear lighting connector
back-up lamps.
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214 Driving and Operating
Tow/Haul Mode
This button is on the instrument
panel, to the right of the steering
wheel.
Pressing this button turns on and off
the Tow/Haul Mode.
This indicator light on the instrument
cluster comes on when the Tow/
Haul Mode is on.
Tow/Haul is a feature that assists
when pulling a heavy trailer or a
large or heavy load. SeeTow/Haul
Mode 0190.
Tow/Haul is designed to be most
effective when the vehicle and
trailer combined weight is at least
75 percent of the vehicle Gross
Combined Weight Rating (GCWR). See
“Weight of the Trailer” inTrailer
Towing 0208. Tow/Haul is most
useful under the following driving
conditions:
. When pulling a heavy trailer or a
large or heavy load through
rolling terrain.
. When pulling a heavy trailer or a
large or heavy load in
stop-and-go traffic.
. When pulling a heavy trailer or a
large or heavy load in busy
parking lots where improved low
speed control of the vehicle is
desired.
Operating the vehicle in Tow/Haul
Mode when lightly loaded or with no
trailer at all will not cause damage.
However, there is no benefit to the
selection of Tow/Haul when the
vehicle is unloaded. Such a
selection when unloaded may result
in unpleasant engine and
transmission driving characteristics
and reduced fuel economy. Tow/
Haul is recommended only when
pulling a heavy trailer or a large or
heavy load.
Conversions and
Add-Ons
Add-On Electrical
Equipment
{Warning
The Data Link Connector
(DLC) is used for vehicle service
and Emission Inspection/
Maintenance testing. See
Malfunction Indicator Lamp
(Check Engine Light) 0103.
A device connected to the DLC —
such as an aftermarket fleet or
driver-behavior tracking device —
may interfere with vehicle
systems. This could affect vehicle
operation and cause a crash.
Such devices may also access
information stored in the vehicle’s
systems.
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Driving and Operating 215
Caution
Some electrical equipment can
damage the vehicle or cause
components to not work and
would not be covered by the
vehicle warranty. Always check
with your dealer before adding
electrical equipment.
Add-on equipment can drain the
vehicle's 12-volt battery, even if the
vehicle is not operating.
The vehicle has an airbag system.
Before attempting to add anything
electrical to the vehicle, see
Servicing the Airbag-Equipped
Vehicle 066 and Adding Equipment
to the Airbag-Equipped Vehicle
0 66.