GMC 2009 Sierra - Manual (Page 107)

Tow/Haul Mode
Your vehicle has a tow/haul mode. The tow/haul mode
adjusts the transmission shift pattern to reduce shift
cycling, providing increased performance, vehicle
control, and transmission cooling while towing or hauling
heavy loads.
Press the button located on the end of the shift lever to
turn the tow/haul on or off. While the tow/haul is on,
a light on the instrument panel cluster comes on.
See Tow/Haul Mode Light on page 3-50 for more
information.
Also see “Tow Haul Mode” under Towing a Trailer on
page 4-41 for more information.
Grade Braking
Grade Braking assists when driving on a downhill grade.
It maintains the vehicle’s speed by automatically
using a shift schedule that lets the engine and the
transmission slow the vehicle. This reduces wear on the
brakes system and increases control of the vehicle.
The system constantly monitors the vehicle’s speed,
acceleration, throttle position, and whether the
brake pedal is being pressed, and determines when to
keep the current vehicle speed or to slow down.
The system then automatically, commands downshifts
that reduce the vehicles speed, until the brake pedal
is no longer being pressed. This indicates the desired
vehicle speed has been reached.
The tow/haul mode and grade braking shift modes can
be activated by pressing the button on the end of
the shift control stalk. While in the Range Selection
Mode, grade braking is deactivated, and lets the driver
select a gear.
See Automatic Transmission Operation on page 2-27 for
more information.
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