GMC 2011 Sierra Owner's Manual page 319

It is very important to know
how much weight your vehicle
can carry. This weight is called
the vehicle capacity weight
and includes the weight of
all occupants, cargo, and all
nonfactory-installed options.
Two labels on your vehicle
show how much weight it was
designed to carry, the Tire and
Loading Information label and
the Certification/Tire label.
Do not load the vehicle
any heavier than the
Gross Vehicle Weight
Rating (GVWR), or either the
maximum front or rear Gross
Axle Weight Rating (GAWR).
This can cause systems to
break and change the way the
vehicle handles. This could
cause loss of control and a
crash. Overloading can also
shorten the life of the vehicle.
A vehicle specific Tire and
Loading Information label is
attached to the center pillar
(B-pillar). With the driver
door open, you will find the
label attached below the
door lock post (striker).