my old landlord has a 2004 silverado with the 5.3. hes a farmer and pulled all kinds of crap with it. i watched him pull a horse trailer out of a frozen puddle, smoking the tires right off it pretty much. ya he abused that truck quite a bit. one day while turning at an intersection pulling a tractor on a trailer his axle broke and came right out! luckily he had the tractor, he lifted the truck up, slid the axle back in then pulled the truck n trailer back quite a ways with the tractor. man when he pulled into his laneway turning left the right axle came out about a foot! craziest thing I ever seen. yup id agree to stay under the 80% max towing weight, I think thats a great rule!