I didn't read all the posts but will input my impressions/experiences. Mine has the 3.73, my trailer loaded is around 8500 - 9k. I live at 4000. Towed from California into Oregon, and never had a problem. When I did that, trailer was fully loaded with household items and truck bed was also fully loaded with household items (furniture, books, etc.). When I approached the mountain grades, I locked it into 3rd and was able to maintain 60 mph at around 3200 rpm. In my opinion it did as good as my old PS 6.0. I was quite pleased. Over the passes I averaged around 8 mpg.