Chevy Duramax 2500HD - 5th Wheel Towing Question

Sport45 wrote:

I wonder how they managed a max king pin rating of 3000# with a max payload of only 2706#?

Because the 3000# rating is a generic maximum number achievable by a base level, regular cab, gas engined 2WD truck.
The 2706# number is the ACTUAL rating for the OPs truck, taking into account it's an extended cab, 4WD diesel.
HUGE difference between the maximum possible numbers available across a specific series of trucks and the number that applies to specific (heavy!) configurations.