I agree, but my Rebel was a 5th gen with a 3.5 lift and 35’s, my 2500 is a 4.5 gen with 2” level and 35’s, not that much bigger than my Rebel, the 6.4 torq should pull the gear. I can cheat a little, by accelerating to a higher speed than needed and then backing off the throttle I can get the trans to shift into 8th between 58-60 and it pulls that no problem , even in ECO mode, at 1500 RPM, but, any uphill grade shifts into 7th until I get level ground again. So it can pull 8th no problem on level ground, but your right about hunting the lower gear on an uphill grade.