2015 GMC SIERRA Owner's Manual

Black plate (70,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
9-70 Driving and Operating
If the trailer turn signal bulbs burn
out, the arrows on the instrument
cluster will still flash for turns. 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
gearbefore starting down a long or
steep downgrade. If the
transmission is not shifted down, the
brakes might get hot and no longer
work well.
Vehicles 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.
The Tow/Haul Mode may be used if
the transmission shifts too often.
See Tow/Haul Mode on page 9-39.
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
transmission in P (Park) for a few
minutes before turning the engine
off. If the overheat warning comes
on, see
Engine Overheating on
page 10-21.
Parking on Hills
{Warning
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 flat surface. If parking the rig on a hill:
1. Press the brake pedal, but do
not shift into P (Park) yet. 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 regular brakes
until the chocks absorb the load.
4. Reapply the brake pedal. Then apply the parking brake and shift
into P (Park).
5. Release the brake pedal.
Leaving After Parking on a Hill
1. Apply and hold the brake pedal.
2. Start the engine.
3. Shift into a gear.
4. Release the parking brake.
5. Let up on the brake pedal.
6. Drive slowly until the trailer is clear of the chocks.

Black plate (71,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Driving and Operating 9-71
7. Stop and have someone pick upand store the chocks.
Maintenance when Trailer
Towing
The vehicle needs service more
often when pulling a trailer. See
Maintenance Schedule on
page 11-3. Things that are
especially important in trailer
operation are automatic
transmission fluid, 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 Towing
If the vehicle has a diesel engine,
see the Duramax diesel
supplement.
If the vehicle is bi-fuel, see the
bi-fuel supplement. Do not tow a trailer during break-in.
See
New Vehicle Break-In on
page 9-23 for more information.
{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, the brakes may not work
well or even at all. 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.
See Vehicle Load Limits on
page 9-15 for more information
about the vehicle's maximum load
capacity.
To identify the trailering capacity of
the vehicle, read the information in
“Weight of the Trailer” later in this
section.

Black plate (72,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
9-72 Driving and Operating
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. Read this section
carefully before pulling a trailer.
Weight of the Trailer
How heavy can a trailer safely be?
It depends on how the rig is used.
Speed, altitude, road grades,
outside temperature, and how much
the vehicle is used to pull a trailer
are all important. It can depend on
any special equipment on the
vehicle, and the amount of tongueweight the vehicle can carry. See
“Weight of the Trailer Tongue”
later
in this section for more information.
Trailer weight rating (TWR) for 1500
series trucks is calculated assuming
the tow vehicle has the driver, a
front seat passenger, and all
required trailering equipment.
Weight of additional optional
equipment, passengers, and cargo
in the tow vehicle must be
subtracted from the trailer weight
rating.
Trailer weight rating (TWR) for
2500 and 3500 series trucks is
calculated assuming the tow vehicle
has only the driver but all required
trailering equipment. Weight of
additional optional equipment,
passengers, and cargo in the tow
vehicle must be subtracted from the
trailer weight rating. Ask your dealer for trailering
information or advice.
For kingpin weight and trailer
tongue weight information, see
“Weight of the Trailer Tongue”
later
in this section.
Use the following chart to determine
how much the vehicle can weigh,
based upon the vehicle model and
options.
Weights listed apply for
conventional trailers and fifth-wheel
trailers unless otherwise noted.

Black plate (73,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Driving and Operating 9-73
VehicleAxle Ratio Maximum Trailer Weight GCWR (a)
1500 Series 2WD Crew Cab Standard Box 5.3L V8 3.234 219 kg (9,300 lb) 6 804 kg (15,000 lb)
6.2L V8 3.234 128 kg (9,100 lb) 6 804 kg (15,000 lb)
1500 Series 2WD Crew Cab Short Box (b) 5.3L V8 3.424 264 kg (9,400 lb) 6 804 kg (15,000 lb)
6.2L V8 3.234 173 kg (9,200 lb) 6 804 kg (15,000 lb)
1500 Series 4WD Crew Cab Standard Box 5.3L V8 3.424 128 kg (9,100 lb) 6 804 kg (15,000 lb)
6.2L V8 3.233 992 kg (8,800 lb) 6 804 kg (15,000 lb)
1500 Series 4WD Crew Cab Short Box (b) 5.3L V8 3.424 173 kg (9,200 lb) 6 804 kg (15,000 lb)
6.2L V8 3.234 037 kg (8,900 lb) 6 804 kg (15,000 lb)
2500 Series 2WD Crew Cab Standard Box
6.0L V8 3.734 445 kg (9,800 lb) 7 257 kg (16,000 lb)
6.0L V8 –Conventional Trailer 4.105 897 kg (13,000 lb) 9 299 kg (20,500 lb)
6.0L V8 –Fifth-Wheel Trailer 4.106 486 kg (14,300 lb) 9 299 kg (20,500 lb)

Black plate (74,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
9-74 Driving and Operating
VehicleAxle Ratio Maximum Trailer Weight GCWR (a)
2500 Series 4WD Crew Cab Standard Box 6.0L V8 3.734 309 kg (9,500 lb) 7 257 kg (16,000 lb)
6.0L V8 –Conventional Trailer 4.105 897 kg (13,000 lb) 9 299 kg (20,500 lb)
6.0L V8 –Fifth-Wheel Trailer 4.106 350 kg (14,000 lb) 9 299 kg (20,500 lb)
3500 Series 2WD Crew Cab Standard Box
6.0L V8 3.734 355 kg (9,600 lb) 7 257 kg (16,000 lb)
6.0L V8 –Conventional Trailer 4.105 897 kg (13,000 lb) 9 299 kg (20,500 lb)
6.0L V8 Fifth-Wheel Trailer 4.106 396 kg (14,100 lb) 9 299 kg (20,500 lb)
3500 Series 2WD Crew Cab Long Box
6.0L V8 (Single Rear Wheels) 3.734 309 kg (9,500 lb) 7 257 kg (16,000 lb)
6.0L V8 (Single Rear Wheels)
Conventional Trailer 4.10
5 897 kg (13,000 lb) 9 299 kg (20,500 lb)
6.0L V8 (Single Rear Wheels)
Fifth-Wheel Trailer 4.10
6 350 kg (14,000 lb) 9 299 kg (20,500 lb)
6.0L V8 (Dual Rear Wheels) 3.734 173 kg (9,200 lb) 7 257 kg (16,000 lb)
6.0L V8 (Dual Rear Wheels) 4.106 214 kg (13,700 lb) 9 299 kg (20,500 lb)
3500 Series 4WD Crew Cab Standard Box 6.0L V8 3.734 264 kg (9,400 lb) 7 257 kg (16,000 lb)

Black plate (75,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Driving and Operating 9-75
VehicleAxle Ratio Maximum Trailer Weight GCWR (a)
6.0L V8 –Conventional Trailer 4.105 897 kg (13,000 lb) 9 299 kg (20,500 lb)
6.0L V8 –Fifth-Wheel Trailer 4.106 305 kg (13,900 lb) 9 299 kg (20,500 lb)
3500 Series 4WD Crew Cab Long Box 6.0L V8 (Single Rear Wheels) 3.734 173 kg (9,200 lb) 7 257 kg (16,000 lb)
6.0L V8 (Single Rear Wheels)
Conventional Trailer 4.10
5 897 kg (13,000 lb) 9 299 kg (20,500 lb)
6.0L V8 (Single Rear Wheels)
Fifth-Wheel Trailer 4.10
6 214 kg (13,700 lb) 9 299 kg (20,500 lb)
6.0L V8 (Dual Rear Wheels) 3.733 992 kg (8,800 lb) 7 257 kg (16,000 lb)
6.0L V8 (Dual Rear Wheels) 4.106 033 kg (13,300 lb) 9 299 kg (20,500 lb)
(a) The Gross Combination Weight Rating (GCWR) is 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.
(b) This model is neither designed nor intended to tow fifth-wheel or gooseneck trailers.
Ask your dealer for trailering information or advice.

Black plate (76,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
9-76 Driving and Operating
Weight of the Trailer Tongue
The tongue load (1) of any trailer is
very important because it is also
part of the vehicle weight. 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 as well as trailer tongue
weight. Vehicle options, equipment,
passengers and cargo in the vehicle
reduce the amount of tongue weight
the vehicle can carry, which will also
reduce the trailer weight the vehicle
can tow.
Trailer tongue weight (1) should be
10–15% and fifth-wheel or
gooseneck kingpin weight should be
15–25% of the loaded trailer
weight (2) up to the maximums for
vehicle series and hitch type.

Black plate (77,1)GMC 2015i Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-8431500) - 2015 - crc - 6/20/14
Driving and Operating 9-77
Vehicle Series Hitch TypeMaximum Tongue
Weight
1500 Weight-Carrying 363 kg (800 lb)
1500 Weight-Distributing 544 kg (1,200 lb)
2500/3500
Standard Box Weight-Carrying or
Weight-Distributing 680 kg (1,500 lb)
2500/
3500 Long Box Weight-Carrying or
Weight-Distributing 907 kg (2,000 lb)
2500 Fifth-Wheel Gooseneck 1 361 kg (3,000 lb)
3500 Single Rear
Wheels Fifth-Wheel Gooseneck 1 814 kg (4,000 lb)
3500 Dual Rear
Wheels Fifth-Wheel Gooseneck 2 495 kg (5,500 lb)
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. Trailer rating may be limited by the
vehicle's ability to carry tongue
weight. Tongue or kingpin weight
cannot cause the vehicle to exceed
the GVWR (Gross Vehicle Weight
Rating) or the RGAWR (Rear Gross
Axle Weight Rating). See
“Total
Weight on the Vehicle's Tires” later
in this section. 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.
If a cargo carrier is used in the
trailer hitch receiver, choose a
carrier that positions the load as
close to the vehicle as possible.
Make sure the total weight,
including the carrier, is no more than
half of the maximum allowable
tongue weight for the vehicle or
227 kg (500 lb), whichever is less.
Total Weight on the Vehicle's
Tires
Be sure the vehicle's tires are
inflated to the inflation pressures
found on the Certification/Tire label
on the center pillar or see
Vehicle
Load Limits on page 9-15. Make
sure not to exceed the GVWR limit
for the vehicle, or the RGAWR, with
the tow vehicle and trailer fully
loaded for the trip including the
weight of the trailer tongue. If using