Like the others, I want to give advice without too many facts, but that doesn't stop us. 7,100 dry weight could easily turn into over 9,000 pounds gvwr. You say you have an eco, but what payload? And how much is left after loading family and stuff? At 9,000 pounds, one would expect to have a tongue weight of over 1,000 pounds which alone may be the problem. Just guessing, like all the rest. Try LT tires, Timbrens or Supersprings, and someone already mentioned a Hensly hitch. Personally, I think you are in F-250 or 2500 tow vehicle range.