I've towed that section of I64 many times, very long grade of several miles at 6% and the last 4-5 at 7%....Towed my 5er up it about a month ago....it'll tax a truck...5er weighed in at 16,200#, I hit the "bottom of the mountain" at 65 mph and topped it at 65 mph, no problem..It's normal when it's hot and humid in that area to see semi's as well as people driving Motor homes, towing TT's and 5er's to be pulled over due to overheating.. I can think of a couple other mountains they could have towed up that would have tested the vehicles also, on I26 and I77, but, the New River Gorge is a long steep run...
appears Chevy hit the highest speeds:)......heck, I know what my truck can do with 16,200# up the mountain and it's more than enough, it's obvious it's the same for the Ford and the Chevy....speed limit is 70 mph and I don't tow that fast, but am half tempted to see if I can top that mountain now at 70, you know just see if it could do it..:)