Westend is correct the max towing is 9800 lbs. with a WD Hitch. It is 5800 without a WD hitch. As also stated, you will most likely run out of cargo capacity before you run out of towing capacity.
The sticker on my F-150 4x4 says Max Cargo is 1411 lbs. This is the important number!!!
The tongue weight on my 5000 lb. TT is 487 lbs. unloaded, add 1000 lbs. food water and other supplies and I now have almost 600 lbs. on the tongue figured at 10%.
Yes the WD hitch does increase the allowable tongue weight but it does not increase the Max Cargo. I add 500 lbs. for two adults and a dog and 200# for my truck cap and I have used 1300 of my 1411 max cargo. This is the dilemma that most people with kids and toys face.
Horsepower can also be a factor; my previous F-150 has a small 200 hp engine which made almost any hill a chalenge.
I hope we have informed not confused. If not ask again, understanding this stuff is important.