I currently have an '04 2500 crewcab that I use to pull a 8,000lb travel trailer (loaded) with a 1,300 lb tongue weight. 6.0L gas V8 with the standard 4.1 rear axle ratio and always use a weight distributing hitch when towing. The max towing capacity for my truck is 8,300lbs. I noticed that the max towing capability of 2500HD (same 6.0L but with a 3.73 rear axle ratio) is 10,200lbs, or almost 2,000lbs more. The suspensions for both the 2500 and 2500HD appear to be the same. Can any one tell me if the extra towing capacity is simply a function of the different axle ratio? Does the 3.73 axle have a higher weight rating?