GMC Yukon Denali 2003 Owner's Manual page 118

Notice: If your wheels won't turn, don't try to drive.
This might happen if you were stuck in very deep
sand or mud or were up against a solid object. You
could damage your transmission. Also, if you
stop when going uphill, don't hold your vehicle there
with only the accelerator pedal. This could overheat
and damage the transmission. Use your brakes
or shift into PARK (P) to hold your vehicle in
position on a hill.
On cold days, approximately 32°F (0°C) or colder, your
transmission is designed to shift differently until the
engine reaches normal operating temperature. This is
intended to improve heater performance.
2-24
Tow/Haul Mode
Your vehicle is equipped with a tow/haul mode. The
button is located on the end of the column shift lever.
You can use this feature to assist when towing or
hauling a heavy load. See "Tow/Haul Mode" under
Towing a Trailer on page 4-47 for more information.
The tow/haul mode also interacts with the Autoride™
feature to enhance the ride when trailering or with
a loaded vehicle. See Autoride™ on page 4-46 .