GMC 2014 Sierra Owner's Manual page 358

The front axle reserve capacity for
the vehicle can be found in the
lower right corner of the
Certification/Tire label, as shown.
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