I think Saluda is steeper. I have never pulled a heavy trailer up Black Mountain. But I go across Mounteagle several times a year. Set cruise at 58, climb at 55 in 4th gear. Jellico is about the same as Mounteagle, maybe a shade less but close. Saluda took 3rd gear. Don't think I was carrying that much (if any) extra weight. As I said above Black Mountain is crooked, much more so than any of the other interstate grades in Southern Appalachia that I've been across.