GMC 2004 Sierra 1500 Pickup Owner's Manual page 368

Tow/Haul Mode
Tow/Haul is a feature on automatic transmission
equipped vehicles that assists when pulling a heavy
trailer or a large or heavy load. The purpose of
the Tow/Haul mode is to:
•
Reduce the frequency and improve the predictability
of transmission shifts when pulling a heavy trailer or
a large or heavy load.
•
Provide the same solid shift feel when pulling a
heavy trailer or a large or heavy load as when
the vehicle is unloaded.
•
Improve control of vehicle speed while requiring
less throttle pedal activity when pulling a heavy
trailer or a large or heavy load.
Automatic transmission equipped vehicles are provided
with a button at the end of the shift lever which when
pressed enables Tow/Haul. When the button is pressed,
a light on the instrument panel will illuminate to
indicate that Tow/Haul has been selected. Tow/Haul
may be turned off by pressing the button again, at which
time the indicator light on the instrument panel will
turn off. The vehicle will automatically turn off Tow/Haul
every time it is started.
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Tow/Haul is designed to be most effective when the
vehicle and trailer combined weight is at least 75% of
the vehicle's Gross Combined Weight Rating (GCWR).
See "Weight of the Trailer" later in the section.
Tow/Haul is most useful under the following driving
conditions:
•
When pulling a heavy trailer or a large or heavy
load through rolling terrain.
•
When pulling a heavy trailer or a large or heavy
load in stop and go traffic.
•
When pulling a heavy trailer or a large or heavy
load in busy parking lots where improved low
speed control of the vehicle is desired.
Operating the vehicle in Tow/Haul when lightly loaded
or with no trailer at all will not cause damage. However,
there is no benefit to the selection of Tow/Haul when
the vehicle is unloaded. Such a selection when unloaded
may result in unpleasant engine and transmission
driving characteristics and reduced fuel economy.
Tow/Haul is recommended only when pulling a heavy
trailer or a large or heavy load.