GMC Yukon XL 2015 Owner's Manual page 246

D (Drive): This position is for
normal driving. It provides the best
fuel economy. If you need more
power for passing, and you are:
Going less than about 55 km/h
(35 mph), push the accelerator
pedal about halfway down.
Going about 55 km/h (35 mph) or
more, push the accelerator all
the way down.
By doing this, the vehicle shifts
down to the next gear and has
more power.
Use D (Drive) and Tow/Haul Mode
when towing a trailer, carrying a
heavy load, driving on steep hills,
or driving off-road. Shift the
transmission to a lower gear
selection if the transmission shifts
too often.
Downshifting the transmission in
slippery road conditions could result
in skidding. See Skidding under
Loss of Control on page 9-5.
The vehicle has a shift stabilization
feature that adjusts the transmission
shifting to the current driving
conditions in order to reduce rapid
upshifts and downshifts. This shift
stabilization feature is designed to
determine, before making an
upshift, if the engine is able to
maintain vehicle speed by analyzing
things such as vehicle speed,
throttle position, and vehicle load.
If the shift stabilization feature
determines that a current vehicle
speed cannot be maintained, the
transmission does not upshift and
instead holds the current gear.
In some cases, this could appear to
be a delayed shift, however the
transmission is operating normally.
The transmission uses adaptive
shift controls. The adaptive shift
control process continually
compares key shift parameters to
pre-programmed ideal shifts stored
in the transmission s computer. The
transmission constantly makes
adjustments to improve vehicle
performance according to how the
Driving and Operating
vehicle is being used, such as with
a heavy load or when the
temperature changes. During this
adaptive shift control process,
shifting might feel different as the
transmission determines the best
settings.
When temperatures are very cold,
the transmission's gear shifting
could be delayed providing more
stable shifts until the engine warms
up. Shifts could be more noticeable
with a cold transmission. This
difference in shifting is normal.
M (Manual Mode): This position
allows selection of a range of gears
appropriate for current driving
conditions. If equipped, see Range
Selection Mode under Manual
Mode on page 9-34.
Caution
Spinning the tires or holding the
vehicle in one place on a hill
using only the accelerator pedal
9-33
(Continued)