2023 GMC SIERRA VEHICLE

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
Driving and Operating 269
.Become familiar with, and follow all state
and local laws that apply to trailer
towing. These requirements vary from
state to state.
.State laws may require the use of
extended side view mirrors. If your
visibility is limited or restricted while
towing, install extended side view mirrors
on your vehicle, even if not required.
.Do not tow a trailer during the first
800 km (500 mi) of vehicle use to prevent
damage to the engine, axle, or other
parts.
.Perform the first oil change before heavy
towing.
.Do not drive over 800 km/h (50 mph) and
do not make starts at full throttle during
the first 800 km (500 mi) of trailer
towing.
.Tow in D (Drive). Tow/Haul Mode is
recommended for heavier trailers. See
Tow/Haul Mode0234. If the transmission
downshifts too often, a lower gear may
be selected using Manual Mode. See
Manual Mode 0232.
If equipped, the following driver assistance
features should be turned off when towing
a trailer:
.Park Assist
.Automatic Parking Assist (APA)
.Reverse Automatic Braking (RAB)
If equipped, the following driver assistance
features should be turned to alert or off
when towing a trailer, unless equipped with
Super Cruise:
.Automatic Emergency Braking (AEB)
.Front Pedestrian Braking (FPB)
If equipped with Lane Change Alert (LCA),
the LCA detection zones that extend back
from the side of the vehicle do not move
further back when a trailer is towed. Use
caution while changing lanes when towing a
trailer.
If equipped with Rear Cross Traffic Alert
(RCTA), use caution while backing up when
towing a trailer, as the RCTA detection zones
that extend out from the back of the vehicle
do not move further back when a trailer is
towed.
{Warning
To prevent serious injury or death from
carbon monoxide (CO), when towing a
trailer: (Continued)
Warning (Continued)
.Do not drive with the liftgate, trunk/
hatch, or rear-most window open.
.Fully open the air outlets on or under
the instrument panel.
.Adjust the climate control system to a
setting that brings in only outside air.
See“Climate Control Systems” in the
Index.
For more information about carbon
monoxide, see Engine Exhaust 0229.
Towing a trailer requires experience. The
combination of the vehicle and trailer is
longer and not as responsive as the vehicle
itself. Get used to the handling and braking
of the combination by driving on a level
road surface before driving on public roads.
The trailer structure, the tires, and the
brakes must all be rated to carry the
intended cargo. Inadequate trailer
equipment can cause the combination to
operate in an unexpected or unsafe manner.
Before driving, inspect all trailer hitch parts
and attachments, safety chains, electrical
connectors, lamps, tires, and mirrors. See
Towing Equipment 0276. If the trailer has
electric brakes, start the combination

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
270 Driving and Operating
moving and then manually apply the trailer
brake controller to check that the trailer
brakes work. During the trip, occasionally
check that the cargo and trailer are secure
and that the lamps and any trailer brakes
are working.
Towing with a Stability Control System
When towing, the stability control system
might be heard. The system reacts to
vehicle movement caused by the trailer,
which mainly occurs during cornering. This is
normal when towing heavier trailers.
Following Distance
Stay at least twice as far behind the vehicle
ahead as you would when driving without a
trailer. This can help to avoid heavy braking
and sudden turns.
Passing
More passing distance is needed when
towing a trailer. The combination of the
vehicle and trailer will not accelerate as
quickly and is much longer than the vehicle
alone. It is necessary to go much farther
beyond the passed vehicle before returning
to the lane. Pass on level roadways. Avoid
passing on hills if possible.
Backing Up
Hold the bottom of the steering wheel with
one hand. To move the trailer to the left,
move that hand to the left. To move the
trailer to the right, move that hand to the
right. Always back up slowly and, if possible,
have someone guide you.
Making TurnsCaution
Turn more slowly and make wider arcs
when towing a trailer to prevent damage
to your vehicle. Making very sharp turns
could cause the trailer to contact the
vehicle.
Make wider turns than normal when towing,
so the trailer will not go over soft shoulders,
over curbs, or strike road signs, trees,
or other objects. Always signal turns well in
advance. Do not steer or brake suddenly.
Driving on Grades
Reduce speed and shift to a lower gear
before starting down a long or steep
downhill grade. If the transmission is not
shifted down, the brakes may overheat and
result in reduced braking efficiency. The vehicle 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.
When towing at higher altitudes, engine
coolant will boil at a lower temperature
than at lower altitudes. If the engine is
turned off immediately after towing at high
altitude on steep uphill grades, the vehicle
could show signs similar to engine
overheating. To avoid this, let the engine
run, 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 0313.
Viewing Systems
If equipped, the viewing systems on the
vehicle can improve visibility while hitching,
backing, and driving with a trailer. See
Driver Assistance Systems 0246.
Parking on Hills
{Warning
To prevent serious injury or death,
always park your vehicle and trailer on a
level surface when possible.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
Driving and Operating 271
When parking your vehicle and your trailer
on a hill:1. Press and hold the brake pedal, but do not shift into P (Park). Turn the wheels
toward the curb if facing downhill or
into traffic if facing uphill.
2. Have someone place chocks under the trailer wheels.
3. Gradually release the brake pedal to allow the chocks to absorb the load of
the trailer.
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.
.Start the engine.
.Shift into a gear.
.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.
Launching and Retrieving a Boat
Backing the Trailer into the Water
{Warning
.Have all passengers get out of the
vehicle before backing onto the sloped
part of the ramp. Lower the driver and
passenger side windows before
backing onto the ramp. This will
provide a means of escape in the
unlikely event the vehicle slides into
the water.
.If the boat launch surface is slippery,
have the driver remain in the vehicle
with the brake pedal applied while the
boat is being launched. The boat
launch can be especially slippery at
low tide when part of the ramp was
previously submerged at high tide. Do
not back onto the ramp to launch the
boat if you are not sure the vehicle
can maintain traction.
.Do not move the vehicle if someone is
in the path of the trailer. Some parts
of the trailer might be underwater and
not visible to people who are assisting
in launching the boat. Disconnect the trailer wiring before backing
the trailer into the water to prevent damage
to the electrical circuits. Reconnect the
wiring to the trailer after removing the
trailer from the water. If the trailer has
electric brakes that can function when the
trailer is submerged, it might help to leave
the electrical trailer connector attached to
maintain trailer brake functionality while on
the boat ramp.
To back the trailer into the water:
1. If equipped, place the vehicle in Four-Wheel Drive High or Automatic
Four-Wheel Drive.
2. Slowly back down the boat ramp until the boat is floating, but no further than
necessary.
3. Press and hold the brake pedal, but do not shift into P (Park) yet.
4. Have someone place chocks under the front wheels of the vehicle.
5. Gradually release the brake pedal to allow the chocks to absorb the load of
the trailer.
6. Reapply the brake pedal. Then apply the parking brake and shift into P (Park).
7. Release the brake pedal.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
272 Driving and Operating
Pulling the Trailer from the Water
To pull the trailer out of the water:1. Press and hold the brake pedal.
2. Start the engine and shift into gear.
3. Release the parking brake.
4. Let up on the brake pedal.
5. Drive slowly until the tires are clear of the chocks.
6. Stop and have someone pick up and store the chocks.
7. Slowly pull the trailer from the water.
8. Once the vehicle and trailer have been driven from the sloped part of the boat
ramp, the vehicle can be shifted from
four-wheel-drive high. Shift into the drive
mode that is appropriate for the road
conditions.
Caution
If the vehicle tires begin to spin and the
vehicle begins to slide toward the water,
remove your foot from the accelerator
pedal and apply the brake pedal. Seek
help to have the vehicle towed up
the ramp.
Maintenance when Trailer Towing
The vehicle needs service more often when
used to tow trailers. See Maintenance
Schedule 0385. It is especially important to
check the engine oil, axle lubricant, belts,
cooling system, and brake system before
and during each trip.
Check periodically to see that all nuts and
bolts on the trailer hitch are tight.
Engine Cooling When Trailer Towing
The cooling system may temporarily
overheat during severe operating conditions.
See Engine Overheating 0313.
Trailer Towing
If equipped with a diesel engine, see the
Duramax diesel supplement.
Caution
Towing a trailer improperly can damage
the vehicle and result in costly repairs
not covered by the vehicle warranty. To
tow a trailer correctly, follow the
directions in this section and see your
dealer for important information about
towing a trailer with the vehicle.
Trailering is different than just driving the
vehicle by itself. Trailering means changes in
handling, acceleration, braking, and
durability. 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.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
Driving and Operating 273
Trailer Weight
{Warning
Never exceed the towing capacity for
your vehicle.
Safe trailering requires monitoring the
weight, speed, altitude, road grades, outside
temperature, and how frequently the vehicle
is used to tow a trailer.
Trailer Weight Ratings
When towing a trailer, the combined weight
of the vehicle, vehicle contents, trailer, and
trailer contents must be below all of the
maximum weight ratings for the vehicle,
including:
.Gross Combined Weight Rating (GCWR)
.Gross Vehicle Weight Rating (GVWR)
.Maximum Trailer Weight Rating
.Gross Axle Weight Rating-Rear (GAWR-RR)
.Maximum Trailer Tongue Weight Rating
See “Weight-Distributing Hitch and
Adjustment” underTowing Equipment 0276
to determine if equalizer bars are required
to obtain the maximum trailer weight
rating. See
“Trailer Brakes” underTowing
Equipment 0276 to determine if brakes are
required based on the trailer weight.
The only way to be sure the weight is not
exceeding any of these ratings is to weigh
the tow vehicle and trailer combination,
fully loaded for the trip, getting individual
weights for each of these items.
A trailering information label on the B-pillar
shows tow rating information for the
vehicle.
{Warning
You and others could be seriously injured
or killed if the trailer is too heavy or the
trailer brakes are inadequate for the load.
The vehicle may be damaged, and the
repairs would not be covered by the
vehicle warranty.
Only tow a trailer if all the steps in this
section have been followed. Ask your
dealer for advice and information about
towing a trailer.
Gross Combined Weight Rating (GCWR)
GCWR is the total allowable weight of the
completely loaded vehicle and trailer
including any fuel, passengers, cargo,
equipment, and accessories. Do not exceed
the GCWR for your vehicle. The GCWR for
the vehicle is on the Trailering Information
Label.
To check that the weight of the vehicle and
trailer are within the GCWR for the vehicle,
follow these steps:
1. Start with the "curb weight" from the Trailering Information Label.
2. Add the weight of the trailer loaded with cargo and ready for the trip.
3. Add the weight of all passengers.
4. Add the weight of all cargo in the vehicle.
5. Add the weight of hitch hardware such as a draw bar, ball, load equalizer bars,
or sway bars.
6. Add the weight of any accessories or aftermarket equipment added to the
vehicle.
The resulting weight cannot exceed the
GCWR value on the Trailering Information
Label.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
274 Driving and Operating
The GCWR can also be confirmed by
weighing the truck and trailer on a public
scale. The truck and trailer should be loaded
for the trip with passengers and cargo.
Gross Vehicle Weight Rating (GVWR)
For information about the vehicle's
maximum load capacity, seeVehicle Load
Limits 0215. When calculating the GVWR
with a trailer attached, the trailer tongue
weight must be included as part of the
weight the vehicle is carrying.
Maximum Trailer Weight
The maximum trailer weight rating is
calculated assuming the tow vehicle has a
driver, a front seat passenger, and all required trailering equipment. This value
represents the heaviest trailer the vehicle
can tow, but it may be necessary to reduce
the trailer weight to stay within the GCWR,
GVWR, maximum trailer tongue load,
or GAWR-RR for the vehicle.
Use the Trailering Information Label to
determine how much the trailer can weigh.
Weights listed apply for conventional trailers
and gooseneck/fifth-wheel trailers unless
otherwise noted.
A step bumper trailer hitch can only support
a total trailer weight up to 2 271 kg
(5,000 lb). If a trailer hitch ball is added to
the step bumper, check the hitch ball rating
to be sure it is higher than the total trailer
weight.
Maximum Trailer Tongue Weight Rating
The Maximum Trailer Tongue Weight Rating
is the allowable trailer tongue weight that
the vehicle can support using a conventional
trailer hitch. It may be necessary to reduce
the overall trailer weight to stay within the
maximum trailer tongue weight rating while
still maintaining the correct trailer load
balance. A fifth-wheel or gooseneck hitch
may support a higher tongue weight.
The Maximum Trailer Tongue Weight Rating
for a conventional trailer hitch or a fifth
wheel/gooseneck hitch is shown on the
Trailering Information Label.
Do not exceed a maximum trailer tongue
weight of 907 kg (2,000 lb) for a
conventional trailer hitch.
The trailer tongue weight contributes to the
Gross Vehicle Weight (GVW). GVW includes
the curb weight of your vehicle, any
passengers, cargo, equipment and the trailer
tongue weight. Vehicle options, passengers,
cargo, and equipment reduce the maximum
allowable tongue weight the vehicle can
carry, which also reduces the maximum
allowable trailer weight.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
Driving and Operating 275
Trailer Load Balance
The correct trailer load balance must be
maintained to ensure trailer stability.
Incorrect load balance is a leading cause of
trailer sway.
The trailer tongue weight (1) should be
10–15% and fifth-wheel or gooseneck tongue
weight should be 15–25% of the total loaded
trailer weight (2). Some specific trailer types,
such as boat trailers, fall outside of this
range. Always refer to the trailer owner’s
manual for the recommended trailer tongue
weight for each trailer. Never exceed the
maximum loads for the vehicle, hitch, and
trailer.The trailer load balance percentage is
calculated as: weight (1) divided by
weight (2) times 100.
After loading the trailer, separately weigh
the trailer and then the trailer tongue and
calculate the trailer load balance percentage
to see if the weights and distribution are
appropriate for your vehicle. If the trailer
weight is too high, it may be possible to
transfer some of the cargo into your vehicle.
If the trailer tongue weight is too high or
too low, it may be possible to rearrange
some of the cargo inside of the trailer.
Do not exceed the maximum allowable
tongue weight for your vehicle. Use the
shortest hitch extension available to position
the hitch ball closer to your vehicle. This will
help reduce the effect of the trailer tongue
weight on the trailer hitch and the rear axle.
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.
Rear Gross Axle Weight Rating
(GAWR-RR)
The GAWR-RR is the total weight that can be
supported by the rear axle of the vehicle. Do
not exceed the GAWR-RR for the vehicle,
with the tow vehicle and trailer fully loaded
for the trip including the weight of the
trailer tongue. If using a weight-distributing
hitch, do not exceed the GAWR-RR before
applying the weight distribution spring bars.
The GAWR-RR for the vehicle is on the
Trailering Information Label.
Ask your dealer for trailering information or
assistance.

GMC Sierra/Sierra Denali 2500 HD/3500 HD Owner Manual (GMNA-
Localizing-U.S./Canada-16504257) - 2023 - CRC - 5/9/22
276 Driving and Operating
Towing Equipment
Hitches
{Warning
In order to avoid serious injury or
property damage, always follow the hitch
manufacturer's instructions when securing
your draw bar/coupling device to the
vehicle's hitch receiver.
Ensure that the draw bar/coupling device
is secured with a locking retainer pin or
other means such that rotation of the pin
or locking mechanism will not cause the
pin to back out or loosen during use.
Failure to correctly secure the draw bar/
coupling device to the receiver can result
in separation of the hitch/receiver while
towing.
Conventional Hitch
A conventional hitch is bolted to the frame
or cross member of the tow vehicle, and is
generally rated Class 2, 3, 4, or 5. Gooseneck Hitch
A gooseneck hitch is designed to be coupled
to a special hitch leveraging a hitch ball, and
is mounted over the rear axle in the
truck bed.
Fifth-Wheel Hitch
A fifth-wheel hitch is mounted over the rear
axle in the truck bed, and leverages a
hinged plate
—the same type of hitch
leveraged by semi trucks. Generally,
fifth-wheel hitches accommodate large
trailers with as many as one, two, or three
axles.
Always use the correct hitch equipment for
your vehicle. Crosswinds, large trucks going
by, and rough roads can affect the trailer
and the hitch.
Proper hitch equipment for your vehicle
helps maintain control of the vehicle-trailer
combination. Many trailers can be towed
using a weight-carrying hitch which has 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 between your vehicle and trailer axles. Fifth-wheel and gooseneck
hitches may also be used. See
“Maximum
Trailer Tongue Weight” underTrailer Towing
0 272 for weight limits with various hitch
types.
Avoid sharp turns when using a step-bumper
hitch to prevent damage. Make wider turns
to prevent contact between your trailer and
your bumper.
Consider using mechanical sway controls
with any trailer. Ask a trailering professional
about sway controls or refer to the trailer
manufacturer's recommendations and
instructions.
Weight-Distributing Hitch and
Adjustment
A weight-distributing hitch may be useful
with some trailers. Use the following
guidelines to determine if a
weight-distributing hitch should be used.