GMC Chevrolet Silverado 2500HD 2021 Owner's Manual page 222

There is also important loading
information for off-road driving in this
manual. See Loading the Vehicle for
Off-Road Driving under Off-Road
Driving 0 211.
Two-Tiered Loading
Depending on the model of the pickup,
an upper load platform can be created
by positioning three or four 5 cm (2 in)
by 15 cm (6 in) wooden planks across
the width of the pickup box. The planks
must be inserted in the pickup box
depressions.
When using this upper load platform,
be sure the load is securely tied down
to prevent it from shifting. The load's
center of gravity should be positioned
in a zone over the rear axle. The zone is
located in the area between the front
of each wheel well and the rear of each
wheel well. The center of gravity height
must not extend above the top of the
pickup box flareboard.
Any load that extends beyond the
vehicle's taillamp area must be properly
marked according to local laws and
regulations.
Remember not to exceed the Gross Axle
Weight Rating (GAWR) of the front or
rear axle.
Add-On Equipment
When carrying removable items, a limit
on how many people carried inside the
vehicle may be necessary. Be sure to
weigh the vehicle before buying and
installing the new equipment.
Caution
Overloading the vehicle may cause
damage. Repairs would not be covered by
the vehicle warranty. Do not overload the
vehicle.
Remember not to exceed the Gross Axle
Weight Rating (GAWR) of the front or
rear axle.
Driving and Operating
* Equipment Maximum Weight
Ladder Rack and 340 kg (750 lb)
Cargo
Cross Toolbox and 181 kg (400 lb)
Cargo
Side Boxes and 113 kg per side
Cargo (250 lb per side)
* The combined weight for all
rail-mounted equipment should not
exceed 454 kg (1,000 lb).
Loading Points
1. Primary Load Points
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