GMC 2009 Yukon XL Owner's Manual page 364

In order to calculate the amount of weight any front
accessory, such as a snow plow, is adding to the front
axle, use the following formula:
(W x (A + W.B.)) /W.B.= Weight the accessory is adding
to the front axle.
Where:
W = Weight of added accessory
A = Distance that the accessory is in front of the
front axle
W.B. = Vehicle Wheelbase
4-42
For example, adding a 700 lb (318 kg) snow plow
actually adds more than 700 lbs (318 kg) to the front
axle. Using the formula, if the snow plow is 4 ft (122 cm)
in front of the front axle and the wheel base is
10 ft (305 cm), then:
W = 700 lb (318 kg)
A = 4 ft (122 cm)
W.B. = 10 ft (305 cm)
(W x (A + W.B.))/W.B. = (700 x (4 + 10))/10 = 980 lbs
(445 kg)
So, if your vehicle's front axle reserve capacity is more
than 980 lbs (445 kg), you could add the snow plow
without exceeding the front GAWR.
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.