so im currently running 35s on a 2012 jku with a dana 30 up front and automatic tranny and i wanna regear cuz i do a solid amount of highway driving/road trips and wanna get my power back.

I have a 1.5" leveling kit and flat flares but probably will bump up to either a 2.5 or 3" lift once i regear.

I need to know, 1. do i only need the overhaul kit like in a Rusty's Gear Special or is there additional equipment required?
&
2. should i gear up 4.88s or 5.13s?

 

What gears are you running right now? For 35s and the 3.6L I wouldn't go more than 4.88s for better offroad use... That engine has plenty of power to turn those tires. I ran 35s with 3.73s on my 2013 and barely noticed a power loss.
When I upgraded to 37s I went 5.13s but I've got d44s.

 

If you have 3.21 gearing, you also need a new carrier in the D30.

The higher the numerical gear, the weaker the ring and pinion become (less teeth = more stress per tooth). With a heavy JKU, I wouldn't go higher than 4.88. I run 4.88 on 37s and on the highway RPMs are a bit higher than I would like (around 2700 at 70). I briefly ran those gears with 35s. I wouldn't run that combo if it were me - unless 37s are in your future. Personal opinion though. You also need to be cognizant of how fast some things are spinning. Driveshafts generally aren't designed to spin constantly above 3000 rpm. If you drive over 70 mph, you're definitely pushing the upper limits.

If you look at a gear chart, look one size down on tires to see what your real world rpm will be like. 35s will roll at about 33.75".

 

Think maybe about 4.56 just a thought.

 

Like others have said before. If you currently have 3.21s you will need the new carrier with thrust washers for your D30 up front. Also look at charts and everything else. I went with 4.88s because i may upgrade to 37s later on and i'm not worried about the whole mpg stuff. I just wanted the power back as i had 3.21s. Yes you should get the overhaul kit as you probably have some miles on your Jeep ( just assuming by the year ). I've talked to Jeep shops and most say if you have very low mileage then no need. I had 5k on mine so i didn't get the overhaul kit just the basic. Also check out 4ws.com and their gear special. They are name brand gears as i bought mine from them as well. Just giving you another site to look at for price comparison.


4.88s would be the gearing i'd go for if you are asking between the 2.