Coby and all,

A 5000lb GVW truck on steep inclines requires a careful hand in managing the
energy of motion.  (Kinetic Energy)

The fizzix of the matter is that the brakes must dissipate as heat the
necessary energy to keep the truck at the selected constant speed with
enough reserve dissipative capability (braking power) to slow or stop the
truck.  It must provide the retarding force equal to the force applied by
gravity and pulling the truck down the hill.

The stock brakes are quite simply marginal in this case.   Upgrading with
better pads increases the dissipative capability but only in the short run.

The pad is an insulator, it is not intended to conduct heat.  Its job is to
be able to create friction on a hot steel surface (disk or drum).  The disk
or drum must be able to dissipate the heat so generated so that the disk
remains in the operating temperature range of the pad.  Better pads only
mean a higher temperature can be tolerated and still remain functional.

The best idea is to upgrade the disks.  The SA kit offered by Overland and
others accomplishes this by achieving a greater dissipation ability due to
it's vented design and larger friction and dissipative surface.

This gives a greater margin of "stopping power" even under downhill
conditions.

"you can whip the cat, but the cat can't haul the piano up a flight of
stairs"

cheers,
pensioner ( it's still just fizzix, it's always just fizzix)  apologies to
Feynmann