2018 GMC SIERRA Owner's Manual

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
272 Driving and Operating
On vehicles with a diesel engine,
Tow/Haul Mode Grade Braking can
be enabled or disabled by pressing
the Tow/Haul Mode button. Use the
exhaust brake and Tow/Haul Mode
for maximum grade braking.
SeeTowing Equipment 0325.
For other forms of grade braking,
see Automatic Transmission 0265
and Cruise Control 0285.Drive Systems
Four-Wheel Drive
If equipped, four-wheel drive
engages the front axle for extra
traction.
Read the appropriate section for
transfer case operation before
using.
Caution
Do not drive on clean, dry
pavement in 4
mand 4n(if
equipped) for an extended period
of time. These conditions may
cause premature wear on the
vehicle’s powertrain.
Driving on clean, dry pavement in
4
mor 4nmay:
. Cause a vibration to be felt in
the steering system.
. Cause tires to wear faster.
. Make the transfer case harder to
shift, and cause it to run noisier.
{Warning
If equipped with four-wheel drive,
the vehicle will be free to roll if the
transfer case is in N (Neutral),
even when the shift lever is in
P (Park). You or someone else
could be seriously injured. Be
sure the transfer case is in a drive
gear —2
m, 4m, or 4nor set the
parking brake before placing the
transfer case in N (Neutral). See
Shifting Into Park 0262.
Caution
Extended high-speed operation in
4
nmay damage or shorten the
life of the drivetrain.
Engagement noise and bump when
shifting between 4
nand 4mor from
N (Neutral), with the engine running,
is normal.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 273
Shifting into 4nwill turn Traction
Control and StabiliTrak off. See
Traction Control/Electronic Stability
Control 0282.
Manual Transfer Case
Move the lever to shift into and out
of four-wheel drive.
An indicator light comes on when
four-wheel drive is engaged. See
Four-Wheel-Drive Light 0153.
N (Neutral) : Use only when the
vehicle needs to be towed.
See Recreational Vehicle Towing
0 430 orTowing the Vehicle 0430.
2
m(Two-Wheel Drive High) : Use
this setting for driving on most
streets and highways. The front axle
is not engaged. This setting
provides the best fuel economy.
4
n(Four-Wheel Drive Low) : This
setting also engages the front axle
and delivers extra torque. Choose
4
nif driving off-road in deep sand,
deep mud, or deep snow, and while
climbing or descending steep hills.
When engaged, keep vehicle speed
below 72 km/h (45 mph).
4
m(Four-Wheel Drive High) : Use
this setting when extra traction is
needed. The front axle engages and
helps when driving on snowy or icy
roads, when off-roading, or when
plowing snow. The vehicle can be shifted between
2
mand 4mwhile the vehicle is
moving. In extremely cold weather,
it may be necessary to stop or slow
the vehicle to shift into 4
m.
Using the Manual Transfer Case
. Use quick motions to shift into or
out of 4
nor N (Neutral).
. Shifting may be harder when the
vehicle is cold, but will return to
normal once warmed up.
. Four-wheel drive reduces fuel
economy.
. Delayed shifts from 4
mto 2mmay
be experienced due to uneven
tire wear, low tire pressure, high
vehicle loading, or cold
temperatures.
Shifting from 2
mto 4m
. Shifts can be made at any
vehicle speed.
. Shift in one continuous motion.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
274 Driving and Operating
.Shifting while the vehicle is in
motion may require that
moderate force be applied to the
shift lever before 4
mcan be
engaged, especially in cold
weather.
. In extremely cold weather, it may
be necessary to slow or stop the
vehicle to shift.
. While in 4
m, the vehicle can be
driven at any posted legal speed
limit.
Shifting In or Out of 4
n
Caution
Shifting the transfer case into 4n
while moving at speeds faster
than 5 km/h (3 mph) may cause
premature wear to the transfer
case, and may cause the gears to
grind.
1. If possible, shift with the vehicle moving 5 km/h (3 mph)
or less. 2. Shift the transmission into
N (Neutral).
3. Shift the transfer case shift lever in one continuous motion.
4. Shifting with the vehicle at a stop may be more difficult. It is
possible that the shift will not
complete and the transfer case
will remain in N (Neutral). This
is normal. To complete the
shift, with the engine running,
shift the transmission to
D (Drive) and back to
N (Neutral), and reattempt the
transfer case shift.
Shifting In or Out of N (Neutral) 1. Have the engine running.
2. Set the parking brake. Press and hold the brake pedal. See
Parking Brake 0281.
3. Place the transmission into N (Neutral).
4. Shift the transfer case lever in one continuous motion into or
out of N (Neutral).
Electronic Transfer Case
Use the transfer case knob, next to
the steering wheel, to shift into and
out of four-wheel drive for extra
traction.
All of the lights will blink on then off
momentarily when the ignition is
turned on. The light that remains on
will indicate the state of the
transfer case.
If the indicator mark on the switch
does not match up with the light
then that likely means the switch
was moved when the ignition
was off.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 275
The indicator mark on the switch
must line up with the indicator light
before a shift can be commanded.
To command a shift rotate the
transfer case switch to the new
desired position. The light will blink
meaning that the shift is in progress.
When the shift is completed the new
position will be illuminated. If the
transfer case can not complete a
shift command, it will go back to its
last chosen setting.
In extreme cold weather it may be
necessary to slow or stop the
vehicle to shift from 2
mto 4m.
Delayed shifts from 4
mto 2mmay be
experienced due to uneven tire
wear, low tire pressure, high vehicle
loading, or cold temperatures.
Caution
Shifting the transmission into gear
before the requested mode
indicator light has stopped
flashing could damage the
transfer case. The settings are:
N (Neutral) :
Use only when the
vehicle needs to be towed. See
Recreational Vehicle Towing 0430
or Towing the Vehicle 0430.
2
m(Two-Wheel Drive High) : Use
for driving on most streets and
highways. The front axle is not
engaged. This setting provides the
best fuel economy.
4
n(Four-Wheel Drive Low) : This
setting engages the front axle and
delivers extra torque. Choose 4
nif
driving off-road in deep sand, deep
mud, or deep snow, and while
climbing or descending steep hills.
When engaged, keep vehicle speed
below 72 km/h (45 mph).
Shifting into 4
nwill turn Traction
Control and StabiliTrak off. See
Traction Control/Electronic Stability
Control 0282.
4
m(Four-Wheel Drive High) : Use
when extra traction is needed. The
front axle engages and helps when
driving on snowy or icy roads, when off-roading, or when plowing snow.
The vehicle can be shifted from 2
m
to 4mwhile the vehicle is moving.
Shifting Into 4
m
Turn the knob to 4mat any speed
up to 121 km/h (75 mph), except
from 4
n. The indicator light will flash
while shifting and will remain on the
selected setting.
Shifting Into 2
m
Turn the knob to 2mat any speed,
except when shifting from 4
n.
Shifting Into 4
n
When 4nis engaged, vehicle speed
should be kept below 72 km/h
(45 mph).
1. The ignition must be on and the vehicle must be stopped or
moving less than 5 km/h
(3 mph) with the transmission
in N (Neutral). It is best for the
vehicle to be moving
1.6 to 3.2 km/h (1 to 2 mph).

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
276 Driving and Operating
2. Turn the knob to 4n. Wait for
the 4
nindicator light to stop
flashing before shifting the
transmission into gear.
If the transmission is in gear and/or
moving more than 5 km/h (3 mph),
the 4
nindicator light will flash for
30 seconds and not complete the
shift. After 30 seconds the transfer
case will shift to 4
m. Turn the knob
to 4
mto see the indicator. With the
vehicle moving less than 5 km/h
(3 mph), and the transmission in
N (Neutral), attempt the shift again.
Shifting Out of 4
n
1. To shift out of 4nthe vehicle
must be stopped or moving
less than 5 km/h (3 mph) with
the transmission in N (Neutral)
and the ignition in on. It is best
for the vehicle to be moving
1.6 to 3.2 km/h (1 to 2 mph). 2. Turn the knob to 4
mor 2m.
Wait for the 4
mor 2mindicator
light to stop flashing before
shifting the transmission
into gear.
If the transmission is in gear and/or
moving more than 5 km/h (3 mph),
the 4
mor 2mindicator light will flash
for 30 seconds, but will not complete
the shift. With the vehicle moving
less than 5 km/h (3 mph), and the
transmission in N (Neutral), attempt
the shift again.
Shifting Into N (Neutral)
To shift:
1. Park the vehicle on a level surface.
2. Set the parking brake and press and hold the brake
pedal. See Parking Brake
0 281.
3. Start the vehicle or turn the ignition on.
4. Shift the transmission to N (Neutral). 5. Shift the transfer case to 2
m.
6. Turn the transfer case knob clockwise to N (Neutral) until it
stops and hold it there until the
N (Neutral) light starts blinking.
This will take at least
10 seconds. Then slowly
release the knob to the 4
n
position. The N (Neutral) light
will come on when the transfer
case shift to N (Neutral) is
complete.
7. With the engine running, verify that the transfer case is in
N (Neutral) by shifting the
transmission to R (Reverse),
then to D (Drive). There should
be no movement of the vehicle
while shifting the transmission.
8. Turn the engine off, and the ignition to ACC/ACCESSORY.
9. Place the transmission shift lever in P (Park). See
Recreational Vehicle Towing
0430.
10. Turn the ignition off.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 277
Shifting Out of N (Neutral)
To shift:1. Set the parking brake and apply the brake pedal.
2. Turn the ignition on with the engine off.
3. Shift the transmission to N (Neutral).
4. Turn the transfer case knob to 2
m.
After the transfer case has
shifted out of N (Neutral), the
N (Neutral) light will go out.
5. Release the parking brake.
Caution
Shifting the transmission into gear
before the requested mode
indicator light has stopped
flashing could damage the
transfer case.
6. Start the engine and shift the transmission to the
desired gear.
Automatic Transfer Case
If equipped, use the transfer case
knob next to the steering wheel to
shift into and out of four-wheel drive.
All of the lights will blink on then off
momentarily when the ignition is
turned on. The light that remains on
will indicate the state of the
transfer case.
If the indicator mark on the switch
does not match up with the light
then that likely means the switch
was moved when the ignition
was off. The indicator mark on the switch
must line up with the indicator light
before a shift can be commanded.
To command a shift rotate the
transfer case switch to the new
desired position. The light will blink
meaning that the shift is in progress.
When the shift is completed the new
position will be illuminated. If the
transfer case can not complete a
shift command, it will go back to its
last chosen setting.
The settings are:
N (Neutral) :
Use only when the
vehicle needs to be towed. See
Recreational Vehicle Towing 0430
or Towing the Vehicle 0430.
2
m(Two-Wheel Drive High) : Use
for driving on most streets and
highways. The front axle is not
engaged. This setting provides the
best fuel economy.
AUTO (Automatic Four-Wheel
Drive) : Use when road surface
traction conditions are variable.
When driving in AUTO, the front
axle is engaged, and the vehicle's
power is sent to the front and rear

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
278 Driving and Operating
wheels automatically based on
driving conditions. This setting
provides slightly lower fuel economy
than 2
m.
Do not use AUTO mode,
if equipped, to park on a steep
grade with poor traction such as ice,
snow, mud, or gravel. In AUTO
mode only the rear wheels will hold
the vehicle from sliding when
parked. If parking on a steep grade,
use 4
mto keep all four wheels
engaged.
4
m(Four-Wheel Drive High) : Use
this position when extra traction is
needed, such as when driving on
snowy or icy roads, when
off-roading, or when plowing snow.
4
n(Four-Wheel Drive Low) : This
setting engages the front axle and
delivers extra torque. Choose 4
n
when driving off-road in deep sand,
deep mud, or deep snow, and while
climbing or descending steep hills. Shifting into 4
nwill turn Traction
Control and StabiliTrak off. See
Traction Control/Electronic Stability
Control 0282.
Shifting Into 4
mor AUTO
Turn the knob to the 4
mor AUTO
position at any speed, except from
4
n. The indicator light will flash
while shifting and will remain on
when the shift is completed.
Shifting Into 2
m
Turn the knob to 2mat any speed,
except when shifting from 4
n. The
indicator light will flash while shifting
and will remain on when the shift is
completed.
Shifting Into 4
n
When 4nis engaged, keep vehicle
speed below 72 km/h (45 mph).
To shift:
1. The ignition must be on and the vehicle must be stopped or
moving less than 5 km/h (3 mph) with the transmission
in N (Neutral). It is best for the
vehicle to be moving
1.6 to 3.2 km/h (1 to 2 mph).
2. Turn the knob to 4
n. Wait for
the 4
nindicator light to stop
flashing before shifting the
transmission into gear.
Caution
Shifting the transmission into gear
before the requested mode
indicator light has stopped
flashing could damage the
transfer case.
If the transmission is in gear and/or
moving more than 5 km/h (3 mph),
the 4
nindicator light will flash for
30 seconds and not complete the
shift. After 30 seconds the transfer
case will shift to 4
m. Turn the knob
to 4
mto display the indicator. With
the vehicle moving less than 5 km/h
(3 mph), and the transmission in
N (Neutral), attempt the shift again.

GMC Sierra/Sierra Denali Owner Manual (GMNA-Localizing-U.S./Canada/
Mexico-11349177) - 2018 - CRC - 10/17/17
Driving and Operating 279
Shifting Out of 4n
To shift:1. The vehicle must be stopped or moving less than 5 km/h
(3 mph) with the transmission
in N (Neutral) and the ignition
on. It is best for the vehicle to
be moving 1.6 to 3.2 km/h
(1 to 2 mph).
2. Turn the knob to 4
m, AUTO,
or 2
m. Wait for the 4m, AUTO,
or 2
mindicator light to stop
flashing before shifting the
transmission into gear.
Caution
Shifting the transmission into gear
before the requested mode
indicator light has stopped
flashing could damage the
transfer case. If the transmission is in gear and/or
moving more than 5 km/h (3 mph),
the 4
m, AUTO, or 2mindicator light
will flash for 30 seconds but will not
complete the shift. With the vehicle
moving less than 5 km/h (3 mph),
and the transmission in N (Neutral),
attempt the shift again.
Shifting Into N (Neutral)
To shift into N (Neutral):
1. Park the vehicle on a level surface.
2. Set the parking brake and press and hold the brake
pedal. See Parking Brake
0 281.
3. Start the vehicle or turn the ignition on.
4. Shift the transmission to N (Neutral).
5. Shift the transfer case to 2
m. 6. Turn the transfer case knob
clockwise to N (Neutral) until it
stops and hold it there until the
N (Neutral) light starts blinking.
This will take at least
10 seconds. Then slowly
release the knob to the 4
n
position. The N (Neutral) light
will come on when the transfer
case shift to N (Neutral) is
complete.
7. With the engine running, verify that the transfer case is in
N (Neutral) by shifting the
transmission to R (Reverse),
then shift the transmission to
D (Drive). There should be no
movement of the vehicle while
shifting the transmission.
8. Turn the engine off, and the ignition to ACC/ACCESSORY.
9. Place the transmission shift lever in P (Park). See
Recreational Vehicle Towing
0430.
10. Turn the ignition to off.