From reading TNX my '07S Auto X should be equipped with a C200 rear and a M180 front geared at 3.13. Right? So I'm thinking into the future and contemplating front and rear air lockers. What is my best path forward now that I understand that the M180 is not the greatest diff to start with and how would it hold up with a locker, or would it or can it? How does the C200 hold up as well equipped with a locker. I will be running 33's with the 3.13 gearing to start with. No Titan swap for now...
Yes, you're rocking a C200k (corporate) rear and R180 with 3.13 gears
The front diff isn't as weak as some would infer. The thing that kills the front diffs is wheelspin with a sudden stop/shock-load... as what happens when an aggressive driver tries to throttle up a slick hill, gets a bit of air in the front (1 wheel) and as the front tire is spinning at full tilt the front makes contact with the ground and SNAP!... A locker (or 2) will greatly limit that. Lockers will mean that you have to use the throttle less.
The greatest benefit to the m205 Titan diff is the mounting flange for the front shafts. Easier to replace a snapped half shaft. Also, if you plan to run big tires and deep gearsets, the larger ring & pinion gear is a benefit. Under 4.10 and you don't 'need' a 205. 4.56 and up and it becomes a need. But with an auto on 33s (i'd argue 35s even) you don't need to go over 4.10 especially if you do mileage. And yes, gears will affect MPG. IMHO 3.54-3.69 is the sweet spot for an auto on 33s. Deeper than that, you get more capability/slower crawl with a cost to MPG and top speed. Your new comfortable highway speed would be 65. If you want to get an idea what it would be like, regularly drive the highway with OD off.
Will a r180 stand up to a locker? Absolutely. Many Frontiers lock the front. Most run ARB F&R, some run an autolocker front, TruTrack rear.
Whether you do auto or selectable front, there's alot to be said for a TT rear. Its always there and gives very little wheelspin. You don't always need 4wd with TT in the rear. If you find yourself hanging out with your rear leg in the air alot, selectable rear may be better, but the TT with traction control is like having a locker... soon as you get it in the air, ABLS stops it and hte TT locks up. Then its all climbing...