GMC 2008 Sierra 1500 Pickup Owner's Manual page 301

Three important considerations have to do with weight:
•
the weight of the trailer
•
the weight of the trailer tongue
•
and the weight on your vehicle's tires
Tow/Haul Mode
Tow/Haul is a feature 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.
•
Increase the charging system voltage to assist in
recharging a battery installed in a trailer.
Press this button at the end of the shift lever to
enable/disable the tow/haul mode.
A light on the instrument
panel will illuminate to
indicate that tow/haul
mode has been selected.
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