I own a 2004 Chevy Silverado 2500HD, 6-liter V8 engine, with the factory towing package. I plan to buy a fifth wheel RV which weighs 12,300 lbs. I believe that Chevy in their literature says 10,100 lbs for a fifth wheel is max. Yet the same truck with a diesel engine is OK by Chevy for towing a 16,100 lbs with a fifth wheel trailer.
My question: is it ok for me to tow this fifth wheel trailer with my truck? I understand that the diesel has much more torque, and that will make for easier towing. So I can go slower uphill. I asked my Chevy dealer chief mechanic about that and he said "as long as you drive it sensibly, and it's a fifth wheel trailer, you should be ok". Also, from a structural point of view (axle load, wheels and tires, etc.), am I endangering anything by towing the heavier then approved fifth wheel trailer?
Double check your owner's manual for the towing capacity numbers. Looking at 2009 figures, there's about a 2,900 lb difference in towing capacities between the same two 3/4-ton GM trucks pulling a fifth-wheel, one with a Duramax and one without.
A truck's towing capacity is determined by a formula which takes into consideration a number of variables. Including, but not limited to, chassis structure (frame strength, wheel base, track, suspension, wheels, tires etc.), engine, transmission, brakes, axle strength, axle ratio and so on. The reasons behind these maximum ratings are to avoid excessive stress on the vehicle in question, and SAFETY.
According to the National Highway Traffic Safety Administration (NHTSA) each year there are approximately 59,000 crashes in the U.S. involving passenger vehicles towing trailers, resulting in about 28,000 people being injured. So, if you want me to say go ahead and tow above the vehicle's maximum capacity, that's not gonna happen. It's best to keep trailer weight at a decent margin below the maximum and allow for extra weight, including cousins and cargo inside the truck which increases the Gross Combined Weight Rating (GCWR).
As far as the diesel difference; when you see higher towing capacities on the same truck with a diesel engine as opposed to gas, there may be more to the equation than better towing ability due to the diesel's exemplary low-end torque. Diesel engines are also built stronger to withstand the non-spark high compression combustion process. Meaning they not only perform well while towing, but they're more durable and last longer than a gas engine under towing conditions. There may also be additional heavy-duty components attached to certain diesels, like a transmission upgrade.