The downside with the 5.0 is that a tune won't give you nearly as much as it would on an EcoBoost. Most 5.0 tunes increase the redline since the Coyote loves high RPMs, but for daily driving that doesn't do too much to help you out as you're not revving it out most of the time.

My $0.02, go for the gears, or if you're up for it, put a supercharger on the 5.0 for more power.

 

I have been thinking about this as well. I’m in an 18 2wd 5.0 with 33’s and 3.15 rear. The power is still ok but I feel like a 3.73 gear would give a nice bump without affecting warranty the way a tune possibly could. The bigger issue is finding a reputable shop close to me to do the swap.

 

You could get a bdx tuner from SCT w/ canned tunes for about $400.00,
with 93 octane tune they claim about a 50 hp/50 ft lbs gain w/the 2018 5.0 .
87 octane tune would be about half of that.

Honestly, though, with 35'' tires you should probably regear with 4.10s or even 4.56s,
then get it tuned.
You could always try just a tune first, Ford left plenty on the table with the 2018 f150 5.0,
but for best results 3.31s are just way to damn tall for those tires.

 

You will feel a bigger change by regearing.

 

Just reprogramming to fix the speedo and shift points will make a big difference, if you haven't done that already. Forscan can help.

 

Tuning won't fix your mathematical loss of torque to the ground. Re-gear it to 4.10 and it'll be like an entirely different truck.

 

As said already, regear to 4.10 minimum, 4.56 would be best especially with the 5.0.

However given the cost difference of each option, try the tune first and see if that's enough for you. But the regear will definitely be more impactful.

 

If this were an older 4-speed truck I would definitely recommend 4.56's. Thats what I put in my '05 when I went to 35's. The truck in this case would have a 6-speed which has much lower 1st and 2nd gears. First is actually slightly over 4:1. In this case, 4.10 gives you plenty of launch capability and you keep a tall overdrive.

 

definitely regear it to 4.10. A tune is not going to be noticeable on the 5.0 in your case.