I towed a 19K pound 5th wheel with a similar 2005....5.9, 3500, 6 speed, 3.73, SRW, chipped. The 5.9 is a brute, no surprise here, and it had no problem pulling, or handling in curves or grades...uphill. Downhill was a different story. The first time out, down a loooong 6% grade in AZ, we ran...