i have a 2012 2wd RCSB STX 5.0 with 3.31 gears and want to upgrade to either a 3.73 or 4.10 posi gears how do i go about this

 

have a good shop do it 4 you

need special equiptment to get the gears perfect so they will last and not hum

the old folks did it by setting it up so the ring and pinion would mark news paper but not tear it but times have changed now with dial indicators so u can make it perfect

 

You will also have to reprogram the PCM for the change in ratio. Dealer can flash for any ratio that was optional on that truck, otherwise you will need a programmer.

 

What if you found a shop that will do it for a good price, but you want to make sure they do a good job? How do you check their work?

 

You will have to get your gears from FoMoCo. Nobody is making aftermarket gears for 2011 and up F150's yet. The shaft on the pinion gear is different than on 2010 and below F150s. It's not a big deal because you can get them through Ford. But it will be more expensive than Yukons or other aftermarket gears. There is a guy on another forum with 40" tires that had some 5.13 gears custom made. I'm sure that wasn't cheap. On the bright side you only need 1 set of gears for your 4x2 so that will make it more affordable.

 

If you question the shop that much, go some where else. But you can pop the diff cover and check the how the gears mesh. I honestly don't know anything about setting up gears, so can't help you past that.