Maximum payload question

I believe that you will find. the brakes are in fact rated to stop the GVWR of the vehicle

Brakes can easily stop a trucks gvwr as the trucks brakes are designed and tested by the truck mfg (before FMVSS testing) to stop the rating of each axle system.
My 2500 Dodge has a 5200 fawr and 6000 rawr = 11200 lbs of braking performance at a minimum. And as was mentioned a 3/4 ton trucks brake systems may be same as their bigger one ton brothers.


NHTSA says this about components of the GAWR:
"Gross Axle Weight Rating is the rated load-carrying capacity of an individual axle and wheel assembly. (It represents the load that may be steadily sustained by the components in the system; i.e., tires, rims, hubs, bearing, axles, brakes, suspension, sub frame, etc. with the GAWR limited by the components with the lowest working rating".

and even rubber mfg mentions brakes ;
RMA

• GAWR: Gross Axle Weight Rating (for each axle) -
The maximum weight rating that the components
(tires, rims/wheels, brakes, springs, and axle) of
each axle are designed to support. This is
determined by the lowest design capacity of any
component. In other words, if the wheels have the
lowest design capacity of any component on that
axle, installing tires with a higher load capacity
does not increase the GAWR. By regulation, the
tire load rating times the number of tires on that
axle must equal or exceed the GAWR for that axle."