GMC 2006 Yukon XL Owner's Manual page 350

Q:
What if I want to add heavier equipment to
my vehicle?
A:
You can add heavier equipment on the front of the
vehicle if you compensate for it by carrying fewer
passengers, less cargo, or by positioning cargo
towards the rear. This has the effect of reducing the
load on the front. However, the front GAWR, rear
GAWR and the gross vehicle weight rating (GVWR)
must never be exceeded.
4-54
CAUTION:
{
On some vehicles equipped with certain front
mounted equipment, such as a snow plow,
it may be possible to load the front axle to
the front GAWR but not have enough weight
on the rear axle to have proper braking
performance. If your brakes can not work
properly, you could have a crash. To help
your brakes work properly when a snow plow
is installed, always follow the snow plow
manufacturer or installer's recommendation
for rear ballast to ensure a proper front and
rear weight distribution ratio, even though the
actual front weight may be less than the front
GAWR, and the total vehicle weight is less
than the GVWR. Maintaining a proper front
and rear weight distribution ratio is necessary
to provide proper braking performance.