I have a 2013 Explorer Limited with the factory tow PKG. I was towing 3 snowmobiles (around 2k lbs with the trailer). the engine will not stay in 5th gear, you`ll be lucky to keep it in 4th most of the time. I wouldn't tow anything more than a large PuP. I`ve seen people tow TT`s with them, I don't know how they do it.
The 4th and 5th gen Explorers are nothing like the 1st and 2nd (and even the 3rd gen for that matter). they are car based. the early ones were more truck based.
BTW, towing anything that heavy in the summer will require more service than normal. the PTU is one major one. they are not serviceable and only hold a 1/2 qt of gear lube. so it gets cooked pretty well being next to the catalytic converter, engine and transmission, towing will only make it worse. I just did the fluid on mine (drilled and tapped for an NPT drain plug. the fluid came out like thick mud! it took 5 drain and fills to get it looking normal. it will be done again at the next oil change. then once a year after that. the water pump is another issue on the 3.5`s.