2020 GMC SIERRA DENALI transmission

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 421
6.6L V8 Engine (L8T) Only
1. Good Battery PositiveTerminal
2. Good Battery Negative Terminal
3. Discharged Battery Remote Positive Terminal
4. Discharged Battery Remote Negative Terminal
The jump start positive post (1) and
negative post (2) are on the battery
of the vehicle providing the jump
start. The jump start positive post (3) and
the negative grounding point (4) for
the discharged battery are on the
passenger side of the vehicle.
The positive jump start connection
for the discharged battery is under a
cover. Slide the cover to expose the
terminal.
1. Check the other vehicle. It must have a 12-volt battery
with a negative ground system.
Caution
If the other vehicle does not have
a 12-volt system with a negative
ground, both vehicles can be
damaged. Only use a vehicle that
has a 12-volt system with a
negative ground for jump starting.
2. If you have a vehicle with a diesel engine with two
batteries, you should know
before you begin that,
especially in cold weather, you
may not be able to get enough
power from a single battery in another vehicle to start your
diesel engine. If your vehicle
has more than one battery,
using the battery that is closer
to the starter will reduce
electrical resistance. This is
located on the passenger side,
in the rear of the engine
compartment.
3. Get the vehicles close enough so the jumper cables can
reach, but be sure the vehicles
are not touching each other.
If they are, it could cause an
unwanted ground connection.
You would not be able to start
your vehicle, and the bad
grounding could damage the
electrical systems.
To avoid the possibility of the
vehicles rolling, set the parking
brake firmly on both vehicles
involved in the jump start
procedure. Put the automatic
transmission in P (Park) before
setting the parking brake. If you
have a four-wheel-drive

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 425
dinghy and dolly towing. Dinghy
towing is towing the vehicle with all
four wheels on the ground. Dolly
towing is towing the vehicle with two
wheels on the ground and two
wheels on a dolly.
Here are some important things to
consider before recreational vehicle
towing:
.Before towing the vehicle,
become familiar with the local
laws that apply to recreational
vehicle towing. These laws may
vary by region.
. The towing capacity of the
towing vehicle. Read the tow
vehicle manufacturer's
recommendations.
. How far the vehicle can be
towed. Some vehicles have
restrictions on how far and how
long the vehicle can be towed.
. Whether the vehicle has the
proper towing equipment. See
your dealer or trailering
professional for additional advice
and equipment
recommendations. .
Whether the vehicle is ready to
be towed. Just as preparing the
vehicle for a long trip, make sure
the vehicle is prepared to be
towed.
Follow the tow vehicle
manufacturer ’s instructions.
Caution
Use of a shield mounted in front
of the vehicle grille could restrict
airflow and cause damage to the
transmission. The repairs would
not be covered by the vehicle
warranty. If using a shield, only
use one that attaches to the
towing vehicle.
Dinghy Towing
(Two-Wheel-Drive Vehicles and
Vehicles with a Single-Speed
Transfer Case)
Caution
If a vehicle with two-wheel drive
or a single-speed transfer case is
towed with all four wheels on the
ground, the drivetrain
components could be damaged.
The repairs would not be covered
by the vehicle warranty.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
426 Vehicle Care
Two-wheel-drive vehicles and
vehicles with a single-speed transfer
case should not be towed with all
four wheels on the ground.
Dinghy Towing (Vehicles with a
Two-Speed Transfer Case)
Only dinghy tow four-wheel-drive
vehicles with a two-speed transfer
case that have an N (Neutral) and a
4
n(Four-Wheel Drive Low) setting.
{Warning
Shifting a four-wheel-drive
vehicle's transfer case into
N (Neutral) can allow the vehicle
to move even if the transmission
is in P (Park). You or others could
be injured. Set the parking brake
and use wheel blocks before
shifting the transfer case to
N (Neutral).
To dinghy tow: 1. Position the vehicle being towed behind the tow vehicle,
facing forward and on a level
surface.
2. Securely attach the vehicle being towed to the tow vehicle.
3. Start the engine.
4. Shift the transfer case to N (Neutral). See “Shifting into
N (Neutral)” underFour-Wheel
Drive 0227. 5. With the engine running,
release the parking brake and
verify that the transfer case is
in N (Neutral) by shifting the
transmission to D (Drive) and
then to R (Reverse). There
should be no movement while
shifting the transmission.
6. Shift the transmission to D (Drive).
7. If equipped with an ignition key, turn the ignition to ACC/
ACCESSORY. If equipped with
Keyless Access, turn the
engine off. Disregard the Shift
to P (Park) DIC message. See
Ignition Positions (Keyless
Access) 0208 or
Ignition Positions (Key Access)
0 210.
{Warning
To avoid death, serious injury,
or property damage, before
dinghy towing the vehicle, always
disconnect and secure the
(Continued)

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Vehicle Care 427
Warning (Continued)
negative battery cable and cover
the negative battery post and
cable with a non-conductive
material. If the battery is left
connected or the battery cable
contacts the post, the Electric
Parking Brake may activate
during towing, which could cause
a crash.
8. Disconnect the negative (–) battery cable. See “Negative
Battery Cable Disconnection”
in Battery - North America
0 358.
9. Shift the transmission to P (Park).
Caution
If the steering column is locked,
vehicle damage may occur. 10. Move the steering wheel to
make sure the steering column
is unlocked.
11. If the vehicle has an ignition key, keep it in the towed
vehicle in ACC/ACCESSORY
to prevent the steering column
from locking. If the vehicle is
equipped with Keyless Access,
keep the RKE transmitter
outside of the vehicle and
manually lock the doors.
Access the vehicle by using
the key in the door lock. See
Door Locks 026.
Disconnecting the Towed Vehicle
Before disconnecting from the tow
vehicle: 1. Park on a level surface. Secure the vehicle with wheel blocks.
2. Re-connect the negative (–) battery. See Battery - North
America 0358. 3. Turn on the ignition with the
engine off. For vehicles with a
key, turn the ignition to ON/
RUN with the engine off. If the
vehicle is equipped with
Keyless Access, with your foot
off the brake pedal, press and
hold ENGINE START/STOP for
five seconds until the green
light comes on in the button.
See Ignition Positions (Keyless
Access) 0208 or
Ignition Positions (Key Access)
0 210.
4. Set the parking brake. See Electric Parking Brake 0233.
5. Disconnect from the tow vehicle.
6. Shift the transmission to N (Neutral).
7. Shift the transfer case to 2
m
(Two-Wheel Drive High). When
the shift to 2
m(Two-Wheel
Drive High) is complete, the
light in the instrument cluster
will stop flashing and stay lit.
See Four-Wheel-Drive Light
0 141.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
428 Vehicle Care
8. Start the engine. Check thatthe vehicle is in 2
m
(Two-Wheel Drive High) by
starting the engine and shifting
the transmission to D (Drive)
and then to R (Reverse). There
should be movement of the
vehicle while shifting.
9. Shift the transmission to P (Park) and turn off the
ignition.
10. Release the parking brake and remove the wheel blocks.
11. Reset any lost presets. The outside temperature
display will default to 0 °C
(32 °F) but will reset with
normal usage.
Dolly TowingCaution
Do not tow this vehicle with two
wheels on the ground, or vehicle
damage could occur. This
damage would not be covered by
the vehicle warranty.
Dolly towing this vehicle is not
allowed with either the front or the
rear tires on the ground for
two-wheel drive or four-wheel drive,
regardless of transfer case.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Service and Maintenance 443
.Lubricate body components. See
Exterior Care 0429.
. Check starter switch. See Starter
Switch Check 0363.
. Check automatic transmission
shift lock control function. See
Automatic Transmission Shift
Lock Control Function Check
0363.
. Check ignition transmission lock.
See Ignition Transmission Lock
Check 0363.
. Check parking brake and
automatic transmission park
mechanism. See Park Brake and
P (Park) Mechanism Check
0 364.
. Check accelerator pedal for
damage, high effort, or binding.
Replace if needed.
. Visually inspect gas strut for
signs of wear, cracks, or other
damage. Check the hold open
ability of the strut. If the hold
open is low, service the gas
strut. See Gas Strut(s) 0365. .
Inspect sunroof track and seal,
if equipped. See Sunroof050.
. Verify spare tire key lock
operation and lubricate as
needed. See Tire Changing
0 407.
. Visually inspect the spare tire to
ensure that it is tightly stowed
under the vehicle. Push, pull,
and try to turn the tire. If the
spare tire moves, tighten as
necessary. See Tire Changing
0 407.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
Service and Maintenance 447
Maintenance Schedule
Additional Required
Services - Severe12 000 km/7,500 mi
24 000 km/15,000 mi
36 000 km/22,500 mi
48 000 km/30,000 mi
60 000 km/37,500 mi
72 000 km/45,000 mi
84 000 km/52,500 mi
96 000 km/60,000 mi
108 000 km/67,500 mi
120 000 km/75,000 mi
132 000 km/82,500 mi
144 000 km/90,000 mi
156 000 km/97,500 mi
168 000 km/105,000 mi 180 000 km/112,500 mi
192 000 km/120,000 mi
204 000 km/127,500 mi
216 000 km/135,000 mi
228 000 km/142,500 mi
240 000 km/150,000 mi
Rotate tires and perform Required Services.
Check engine oil level and oil life percentage.
Change engine oil and filter, if needed. Check
engine air filter life percentage and status.
Change engine air filter, if needed.
@ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @
Replace passenger compartment air filter. (1)@ @@@@@
If the vehicle is not equipped with the engine air
filter life system, replace engine air cleaner
filter. (2)@ @@
Inspect evaporative control system. (3)@@@
Replace spark plugs. Inspect spark plug wires.
(Except 2.7L L4 Turbo Engine)@
Replace spark plugs. Inspect spark plug wires.
(2.7L L4 Turbo Engine Only)@ @
Change automatic transmission fluid and filter.@@@
For GVW under 3 900 kg (8,600 lb), change
transfer case fluid, if equipped with 4WD. (4)@@@
For GVW over 3 900 kg (8,600 lb), change
transfer case fluid, if equipped with 4WD. (4)@@@@@@
Drain and fill engine cooling system. (5)@
Visually inspect accessory drive belts. (6)@
Replace brake fluid. (7)
Replace windshield wiper blades. (8)
@ @ @ @ @ @ @ @ @ @
Replace hood gas struts and tailgate
dampener. (9)@ @
Replace air conditioning desiccant. (10)

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-13337776) - 2020 - CRC - 8/27/19
452 Service and Maintenance
Recommended Fluids, Lubricants, and Parts
Recommended Fluids and Lubricants
This maintenance section applies to vehicles with a gasoline engine. If the vehicle has a diesel engine, see
“Recommended Fluids and Lubricants”in the Duramax diesel supplement.
Fluids and lubricants identified below by name, part number, or specification can be obtained from your dealer.
Usage Fluid/Lubricant
Automatic Transmission (6-Speed Transmission) DEXRON-VI Automatic Transmission Fluid.
Automatic Transmission (8-Speed Transmission) DEXRON-HP Automatic Transmission Fluid.
Automatic Transmission (10-Speed Transmission) DEXRON ULV Automatic Transmission Fluid.
Chassis Lubrication Chassis Lubricant (GM Part No. 12377985, in Canada 88901242) or lubricant meeting requirements of NLGI #2, Category LB or GC-LB.
Engine Coolant 50/50 mixture of clean, drinkable water and use only DEX-COOL coolant. SeeCooling System 0346.
Engine Oil Engine oil meeting the dexos1 specification of the proper SAE viscosity grade. ACDelco dexos1 full synthetic is recommended. See Engine Oil
0 339.
Front and Rear Axle Driveshaft Splines Spline Lubricant, Special Lubricant (GM Part No. 19257121, in
Canada 19257122).