"Went through three passes all around 4300 ft"
The ones I went through were 10,000 - 11,000, so that might be the difference. The drvier's seat gave me a back ache at first, but now after a few months and 7,000 miles, either the seat has broken in to fit my back, or my back has broken in to fit the seat. In either case, I find the seat much more acceptable than when I first bought it.
When going uphill I kept the O/D locked-out the entire time.