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.
Your vehicle’s transmission uses adaptive shift controls.
Adaptive shift controls continually compares key shift
parameters to pre-programmed ideal shifts stored in the
transmissions computer. The transmission constantly
makes adjustments to improve vehicle performance
according to how the vehicle is being used, such as
with a heavy load or when 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 Allison
Transmission
®
and Hydra-Matic
®
6-Speed
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.
MANUAL MODE (M):
This position, is available on
vehicles with the Allison Transmission
®
or Hydra-Matic
®
6-Speed transmission. It lets drivers select the range
of gears appropriate for current driving conditions.
If your vehicle has this feature, see Range Select Mode
(Allison Transmission
®
or Hydra-Matic
®
6-Speed
transmission) later in this section.
THIRD (3):
This position is also used for normal driving.
It reduces vehicle speed more than DRIVE (D) without
using the brakes. You might choose THIRD (3)
instead of DRIVE (D) when driving on hilly, winding
roads, when towing a trailer, so there is less shifting
between gears and when going down a steep hill.
SECOND (2):
This position reduces vehicle speed
even more than THIRD (3) without using your brakes.
You can use SECOND (2) on hills. It can help control
your speed as you go down steep mountain roads, but
then you would also want to use the brakes off and on.
If you manually select SECOND (2) in an automatic
transmission, the transmission will start in second gear.
You can use this feature for reducing the speed of the
rear wheels when you are trying to start your vehicle
from a stop on slippery road surfaces.
2-31
Summary of Contents for Sierra 2008
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