I have a 2020 f150 supecab 4x4. It is the STX package so pretty basic. I live in SE Texas and frequently make trips to the hill country and west Texas. 90% of my trips are pulling either a 16’ trailer with a UTV, a 20’ with two UTVS, or a 35’ camper. The truck came factory with a 3.31 gear. I recently noticed my rear end leaking from the front seal and a clunking feeling at initial takeoff. Going to have the rear end rebuild and while I am in there go ahead and re-gear to a lower ratio the 3.31 is not good while towing. Generally have to lock it out of 9 and 10th gear and it still wants to stay in 7th. Anyone have a similar truck with either a 3.73 or 4.10 with some input. I will be replacing the gears in the front end as well.

 

Since you have a 4x4 you'll need to research your front diff to match. Just FYI

 

You may spare a gear (maybe not), but a few hundred extra RPMs for the cost is just tossing money away just to do it. Towing of any consequence generally won’t happen in OD, anyway.

 

You didn't say what engine and if your tires are stock. If a 3.5 Ecoboost with stock tires, I wouldn't regrear it. Max tow on an Eco is 3.55. I tow 10k lbs with a max tow and stock tires. I turn off gears 8-10 while towing. Max towing capacity with a 3.5 Eco with 3.31 is still around 10k lbs.
If you have a 5.0 and/or larger tires, regrear it to 3.73 or 4.10 depending on tire size and engine.

 

It is a 5.0. Stock size tires for now. Going to get 33s or 35s with a lift soon

 

Regearing seems pointless with 10 gears to choose from regardless of tire size. 1st gear has plenty of grunt regardless of drive ratio. You just spend more time in 10th gear instead of 9th at cruising apeed with bigger gears but the final ratio (rpm) will end being about the same. Even with the 6r80, it rarely made sense as that had a rather low 1st gear as well.

Different story for my 2004 4 speed 4.6l, however.

 

4.10 is your answer based on the 5.0 and future tires.
Oh, one more thing. Check your axle. If it is an 8.8, you are asking for trouble to tow that 35' camper regardless of gear ratio. An 8.8 won't handle the heat.