A friend and I have went to the desert Southwest the last couple winters. He has a 2004 2500 6.0 with the 4 speed auto. The first downshift isn't bad but on the second one will jump to over 4,000 RPM and it sounds like it will self destruct and isn't getting anywhere. We have the same campers and my old 95 one ton dodge will go over the same mountain and not shift out of overdrive. Having said that I believe the newer 6.0's with the 6 speed do a lot better. I would consider one of those instead of a modern muffler juice DPF diesel when they get affordable.