I'm going to be running 40" tires, I'm looking at 4:88 gears, I do have the FX4 package, is there anything special about changing gears or is it business as usual?
You can buy the gear sets aftermarket or oem. If you have never done it pay someone to do it for you. But, you can get a complete install kit with bearings ring and pinion and seals. You will need to know how to set pinion depth and ring gear to pinion tooth mesh pattern.
Nitro Gear and Axle has 4.10 and 4.30 gears availible for the 2011+ trucks with the 37 spline pinions for about half the price of OEM. 4.30 gears and 40s should put you pretty close to the same rpm as 3.55s and 275/70r18s. As far as I know no one makes anything lower than a 4.30 gear for the new truck. I have also heard that its only the 350s with the larger spline where the 250s still have the same 31 splines as previous, anyone know if thats true or not?