The gross weight rating is a number that the manufacturer calculates based on the stock equipment on the vehicle when it left the factory. All the 2500/3500 trucks have a rear axle that is rated for at least 8900 lbs. and limited only by the rims and tires.
Stock tires are load rated for these trucks at from 2800-3200 lbs. per tire but you can buy after market tires rated at 3750 for your rims or go to 19.5 rims and tires and be in the 4400 or more per tire load capacity. Big difference between two tires that support 6400 lbs. at the rear and two tires that can support 8800 lbs. at the rear.
