GMC 2003 Sierra 1500 Pickup Owner's Manual page 342

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
-t-
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
For example, adding a 700 Ib. (318 kg) snow plow
actually adds more than 700 Ib. (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:
A = 4 ft. (122 cm)
W.B. = 10 ft. (305 cm)
980 Ib. (445 kg)
So, if your truck's front axle reserve capacity is more
than 980 Ib. (445 kg), you could add the snow plow
without exceeding the front GAWR.
W
=
700 Ib. (318 kg)
(W
X
(A
+
W.B.))/W.B.
=
(700
X
(4
+
10))/10 =
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