Ricktwuhk

You cannot increase your Payload. 1,110 - 100 for the hitch = 1010. 1010 /.13 = 7,769. Max loaded.

But, your payload may limit you to less depending on load.

chimmike

3.31s and the 6sp auto trans will be miserable towing a travel trailer or any sort of trailer with aerodynamics of a brick. Gearing makes all the difference in the world on that 6sp. 3.55s or even 3.73's won't be too aggressive, and at least 3.55's should not affect your mpg much, if at all.

smokeywren

Yeah, you have enough power and torque and cooling capacity to tow up to your tow rating of a bit over 10,000 pounds. But the tow rating is not your limiter as to how heavy a trailer you can tow without being overloaded. Your F-150 has the 4x4 drivetrain and the heavy luxury stuff of the 302 equipment pkg,. Your GVWR is the same as any other F-150 with the same cab and bed, so your payload capacity is reduced to haul that front differential and luxury stuff around. Ricktwuhk gave you the numbers, but understand that the 7,769 max trailer weight he calculated assumes absolutely no payload in the truck except hitch weight. So if you haul people, pets, tools and camping stuff in the truck, you cannot tow even a 7k trailer without being overloaded over the GVWR of your truck.

I don't agree with the others that say you need more axle ratio. My 2012 F-150 with the 3.5L EcoBoost engine and 3.15 axle would tow a 7k trailer without even realizing it was back there. It towed my 9k 5er on a couple of trips with no problems. And one time I towed a 21k loaded equipment trailer across the central Texas Hill Country without breaking a sweat. So you probably don't need a different axle ratio, but understand that when those twin turbos go to work, your MPG goes into the gutter. Mine averaged about 10 MPG when towing my 5k TT, 9 MPG when towing my 9k 5er, and only 6 MPG when towing that 21k trailer. So hold off on replacing the ring gears and pinions in the differentials until after at least one long towing trip when loaded to the gills. Then decide if you really want to spend at least a coupla grand to change to shorter legs in the drivetrain.

Flamingtaco

Smokeywren is on the money, the 3.5eco has pretty solid torque and can handle a lot in any gearing. The taller diffs will present less work to the engine, but you can deal with that when you need to by locking out 6th, or even 5th. If you are towing hundreds of miles every weekend, I'd say go for taller diffs, but if you are towing your vette 5-10 times a year to shows and track, and lay down real miles in an unloaded daily commute, 3.31 is a good compromise between mpg and raw wheel torque.