GMC 2002 Yukon XL Owner's Manual page 309

2. Position the jack under the vehicle. If the flat tire
is on the front of the vehicle, position the jack on
the frame behind the flat tire where the frame
sections overlap.
On all 1500 series vehicles, use the jacking pad provided
on the rear axle. On 2500 series vehicles, use the axle
between the spring and shock.
If you have added a snow plow to the front of
your vehicle, lower the snow plow fully before raising
the vehicle.
5-26
CAUTION:
Getting under a vehicle when it is jacked up is
dangerous. If the vehicle slips off the jack, you
could be badly injured or killed. Never get under
a vehicle when it is supported only by a jack.
CAUTION:
Raising your vehicle with the jack improperly
positioned can damage the vehicle and even make
the vehicle fall. To help avoid personal injury and
vehicle damage, be sure to fit the jack lift head
into the proper location before raising the vehicle.