GMC 2001 Sierra 1500 Pickup Owner's Manual page 272

D
The total weight of any additional cargo you intend
to carry.
Say, for example, you have a 700 lb. (318 kg) snow
plow. The total weight of all occupants and cargo
inside the cab should not exceed 300 lb. (135 kg).
This means that you may only be able to carry
one passenger. But, even this may be too much if
you've got other equipment already adding to the
weight of your vehicle.
Here are some guidelines for safely carrying a
snow plow on your vehicle:
D
Make sure the weight on the front and rear axles
doesn't exceed the axle rating for each.
D
For the front axle, if more cargo or passengers
must be carried, appropriate counter ballast must be
installed rear of the rear axle. Counter ballast must
be properly secured so it won't move during driving.
4-50
D
Follow the snow plow manufacturer's
recommendations regarding rear ballast.
Rear ballast may be required to ensure a proper
front and rear weight distribution ratio, even
though the actual weight at the front axle may be
less than the front axle rating.
D
The snow plow manufacturer or installer can
assist you in determining the amount of rear ballast
required, to help make sure your snowplow/vehicle
combination does not exceed the GVW rating, the
front and rear axle ratings, and the front and rear
weight distribution ratio.
D
The total vehicle must not exceed the GVW rating.