Your using the trucks GVWR to figure axle/tire load capacities.
Other folks use the trucks 6200 RAWR to figure how much pin weight the rear axle will carry.
Your single 7680 gross weight is of little use for this method. Separate front and rear axle weights are required. That way you know if the rear axle is overloaded.
Example...... GM rates the 2500 trucks rear axle at 6200 RAWR. The front axle will carry little if any pin weight. The 4x4 Dmax/A rear axle may weigh approx 2800 lbs before loading. This gives you approx 3200 lb payload. Now figure 200 lbs for hitch and rails and another 200 for gear and a percentage of occupants which leaves the truck with approx 2700-2800 lbs for a "wet" pin weight.
IMO your 310 lbs of occupants may = 150-175 lbs on the rear axle.
If it was my truck I would load it like its to be used and get separate front and rear axle weights like GM suggests. That way regardless of RAWR or GVWR method you will know how much pin weight sits on the trucks rear axle/tires.
JIMNLIN, I think I am understanding the information differently. I had understood, perhaps altogether incorrectly, that these are two separate "tests", and one is the one you are referencing, and the other is the tow vehicle GVWR "test". My sense is that GM is saying 10,000 lbs. is tops, regardless of other "passing" factors. After I got the CAT results, I knew this was not going to turn out favorably. Thanks for your comments.
Unless I am missing something, it appears I would exceed the Chevrolet recommended gross vehicle weight rating if I buy any of the 2013 Montanas (standard Montana). Had to cancel an order on a new, new Montana 3150rl when the updated specs were finally posted by Keystone to the web.
Please let me know if I am looking at this incorrectly, but this is what I see. I have a 2011 Silverado 2500HD Duramax 4x4 Z71 with the truck gross vehicle weight rating capped at 10,000 lbs. With fuel tank topped off and only the Reese fifth wheel hitch as added weight (no passengers, nothing else), the CAT scale says the gross truck weight is 7,680 lbs. If we add in the passenger weight of 310 lbs, this leaves a grand total of 2,010 for king pin weight. Poof goes the Montana idea.
While there are a great many positives about the 2500HD, the 10,000 GVWR and increasing king pin weights seem to cut to the quick.