I think I have it mostly figured out from my research. I have a 2012 Jeep Wrangler Sahara with the 321 gears. It is a 6 speed with 18" with 35" tires. I drive about 70 miles highway daily to work. I was looking to change the gears to 4.1 or 4.56 because of the power loss on hills. I guess I need to change the Carrier or put in a locker. I have a shop that will help me with the install if I get the parts so I want to make sure I have everything ordered before we get started. So now for the questions
1. 4.1 or the 4.56 gears?
2. Do I need to change both the front and rear carriers? I see most carriers are just the housings do I need new gears for the inside of the carrier? or
3. Should I Just put lockers instead of messing with the carriers? If so what one would be the best on a low budget?
4. Is there any thing else I will need other then the minimum installation kit and fluids because the jeep only has like 4,000 miles?

I think I have all the questions and info needed covered if there is anything I am missing let me know. Any and all help would be greatly appreciated...

 

If you are staying with 35's go with 4:10's 37's then 4:56 might make better sense. You need to do both the front and rear gears. You do not have to change the carrier unless you want to do lockers at about 600 to 1000 each depending on the locker. The up side of doing a locker now is not paing to install them later saving 600 to 1000 depending on your area labor rates. Another option is getting a set of used Rubi axles with 4:10's and lockers installed.

 

wtih 3.21's you do need to change the front carrier if going higher gearing.

 

So is it just the front carrier that needs to be changed?

 

Yeah just the front, now would be the time to install lockers or LSDs, depending on your needs. Installing them now will save you the cost of install later