I tow a 7' wide, 7' height and 14.5' long horse trailer, with my 4x4 SE kc2008. Empty weight is about 2800lbs. It's not a Vnose, but not straight one. When backwind, following a truck or downhill, I use overdrive loaded or empty. So I use overdrive only when truck don't shift everytime, and when conditions give it chance to maintain speed. I have electric brake on both axles. It's a must. Since last summer, I use a weight distributing hitch. A realy good purchase for me. Don't have any trouble on hills. Braking is good enough with trailer brakes. Change my diff fluid at 26000 km (16500 miles). Wanna give it all better conditions I can. Keep an eye on tranny, but fluid looks great. Don't have any overheating problem with both engine or tranny. But we almost never went over 30 celcius (90 F). I tow from 1 to 6 hours in a row without trouble.
Keep en eye on tire pressure (truck and trailer) bearing and brakes on trailer, don't use your truck like a GM3500 duramax, place your cargo correctly (weightr distribution) and all shoulb be great.
total weight with 2 horses, my dog, girlfriend and all cargo is about 5500lbs. Everything is allright