GVWR as stated by the manufacturer: 1) Is very conservative; 2) Is based on the configuration of the vehicle AS THEY SOLD IT. Note - manufacturers (unless you are specifically buying an HD vehicle -which will have an expected harsh ride), install softer suspension, undersized tires, and too soft sidewalls for the purpose of making a truck ride more like a car - to influence the woman's experience because if men and women shop together - it is the woman's opinion that carries by far the most weight in the purchasing decision. Of course, when they do this - there is the follow on of weaker-than-should-be parts installed on said vehicle.
//
A 1/2 ton truck with 265x70-17 P-Rated tires, 3.23:1 gears, base rate springs, 11"-12" discs, and 1/2" tie rods - will be very pliable and soft-riding (translation = comfortable ride) and the associated GVWR will be based on that config. If you start changing components: E-rated tires, steeper gearing, stiffer springs, bigger brakes, stronger/thicker/bigger steering components, etc - the vehicle will handle that max GVWR in a much more efficient and safe manner, but will also increase the vehicle's ability to handle additional weight as well.
//
Think of it in terms of the human body - a typical male 5'10" tall, 180# - who doesn't TRAIN - say can bench press 190# and squat 225#. Now - take that same human and turn him into a bodybuilder who trains, eats better, and builds his body (increasing muscle, strengthening bones, joints, tendons) - and now that person can move that same amount of weight with much less effort and more stability, or can move substantially more weight because his body has been modified for the purpose. Or, think of a race car - better stuff equates to increased performance and capability.
//
Having said that, it is far more cost efficient to start with a more purpose built platform to begin with (less modifications necessary) - but I would not say that you cannot increase the GVWR (not official increase, but practical increase) capability of a vehicle with the proper modifications.
//
My 1/2 ton Avalanche 4x4 came factory with 4.10 gears (instead of 3.73), a higher capacity air filter, Z-71 springs (instead of base) - everything else in the engine, frame, diff, brakes, P-Rated tires, etc was exactly the same as a base model - and my listed GVWR is ~100# more than a base model.
//
Since then, I have modded it to have: 1.5" tie rods (stock 1/2"), larger brake discs and calipers, larger tires E-rated, 4.88 gears, Hummer springs, aftermarket front and rear control arms, aftermarket pitman & idler arms with additional bracing, additional separate coolers (rather than integrated), 100% aftermarket transmission and torque converter, headers, bigger exhaust, higher capacity air intake, performance tuner, aftermarket suspension, strengthened the differential, and welded in sliders along the frame - which have the added benefit of strengthening the widest (most vulnerable) portion of the frame. My truck now makes 22% more HP and 30% more torque. More importantly, it makes that torque much lower in the RPM band than stock so I don't have to wind up the engine to get it.
//
Point being - you can modify a vehicle to increase it's capability - to a point - but most of my mods could have been avoided if I had started with a 3/4 Ton HD platform to begin with. Oh well - I'm stubborn.
). Part of it is probably the tires, but is there thicker steel on the frame? Is the rear end bigger (that's probably more a function of the engine output), etc.? I know the suspension may be part of it for sure.
