That sounds about right. I am at about 6000 RPMs at 40 MPH. I try not to go beyond 5500 RPMs because the AC shuts off and the power begins to diminish.
I don't know how much difference 4.56 gears makes as they are OEM for Power Wagons and therefore I have had them from the start. On some of the Dodge forums the guys that make the switch seem to be quite impressed. Hannibal on this forum had a 2005 Ram that he switched from 3.73s to 4.56s and seemed happy with the results.
I looked back through your posts and see you are pulling 7% to 8% grades. On grades like that I will most likely be in first gear as well.
This is the downhill side, but I had to return the same route.
