My sister and brother in law have a 3.5 Ecoboost EL and they tow a 6000 lb gross weight trailer with it. I'm sure they're over their GVWR with it loaded to camp when you add in the tongue weight, dog, three kids, two adults, coolers, etc., but it does okay with the load. They don't tend to tow long distances or go very fast.
I don't recall the axle ratings off hand, but the payload on it is pretty silly - 1350 lbs or so. I remember because it because it's the same as my wife's Pilot. It is a pretty loaded model.