Hummer 2009 H2 - Manual (Page 120)

2 (Second): This position reduces vehicle speed
without using the brakes. Use 2 (Second) on hills.
It can help control vehicle speed as you go down steep
mountain roads, but then you may also want to use
the brakes off and on.
1 (First): This position reduces vehicle speed without
using the brakes. Use it for major/severe downgrades
and off-road driving where the vehicle would otherwise
accelerate due to steepness of grade.
When you shift to 2 (Second) or 1 (First) it provides
the lowest gear appropriate to your current road speed
and continues to downshift as the vehicle slows,
eventually downshifting to the selected gear.
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 will be 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 may appear to
be a delayed shift, however the transmission is operating
normally.
The transmission uses adaptive shift controls that
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
vehicle is being used, such as with a heavy load or
when the temperature changes. During this adaptive
shift control process, shifting may feel different as the
transmission determines the best settings.
When temperatures are very cold, the Hydra-Matic ®
6L80 automatic transmission’s gear shifting may
be delayed providing more stable shifts until the engine
warms up. Shifts may be more noticeable with a cold
transmission. This difference in shifting is normal.
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