Our 2003 Jayco 31' is probably a little lighter than the Four Winds, but on the same E450. We went from a 1988 Japanese minitruck to a 2009 version which is now more midsize. Towed weight went from 2500# to 3500# and we can definitely feel it. Downshifts more and has to work harder in general. And that's only in Flat Florida. Yes, 5000# max tow rating is common on Class C's with Ford chassis. But I gotta say from my experience you'd be happier with a toad around 3000#.
EDIT: Curb Weight for 2014 Grand Cherokee was listed 4545# on Edmunds. I'd trust that options might drive that number higher.