My 2003 Sierra HD crew cab pickup overheats when I pull my toy hauler, especially in hilly terrain. I bought the truck new, have take care of it, and it only has 80,000 miles on the odometer. I pull a small toy hauler with motorcycle in the back. It overheats on hills and when going slow in traffic. And, the AC only works well when I’m traveling at highway speeds. The engine is solid, always changed oil at 3k and it never uses a drop of oil. My question is: can I do anything to fix the overheating problem, bigger radiator, etc? I’ve had the current radiator flushed and refilled accordin