I live in Florida. Have a 2012 5 SPd auto 3.21 on 35" KM2s.

Thinking about regearing to tow a small pop up camper and twice a year trips to NC mountains. Camper is not taken to the mountains. Need to run highway packed with gear.

KM2s run small-ish. I am stuck between going with 4.10s and 4.56.

I will never go to 37" tire on the front Dana 30. Seems that 12+ Rubicons do just fine with 35s and 4.10s. My buddy has a 13 Rubi with 35 KM2s an runs 2500 RPM at 70. I think any higher would be hard on the engine and kill my MPGs....?

 

If it were mine I would go no lower than the 4:10's, possibly 3:72s for street driving.

 

I'm running the factory 4:10's with 35's on a '12 auto and its fine. In the green on the gearing charts.

 

I'm getting gears done in 2 weeks and the mechanic keeps pushing 4.88 you think that's to much for 35s?

 

DEPENDS how and where you do most of your driving. If you have a heavy foot then 4.88 is better. If you are tame and feel fuel efficiency is important go 4:10. I was running 4:10's with 30" tires and it was slow and lame to me. But hey, I"m a power freak...hemi transplant in process. Just depends if you want it to be fun in town or good on the highway. Go 4:88 or 5:10.

 

Again, just to be clear, OP is running a 2012. Please check the gearing charts.

 

I'd go 4.56 if I were going to spend the money on the install... the bump from 4.1 to 4.56 isn't that big so you won't have a huge mileage drop off. If you are going to spend the money go one step past the Rubi

 

Most shops (around me at least) push for 4.88's for two reasons... 1) they stock that gear more than 4.1 or 4.56, and 2) its an expensive install and they don't want you to be upset with a small bump after paying so much

The only person I have ever met who felt his JK was over geared was running the 3.8l 35's and had 5.13 gears 6MT... he got good mileage on the highway (all things considered) but he hated it on the street b/c he had to shift gears like 3 times before he hit 20 miles per hour... I bet in an auto it wouldn't be that bad.

 

4.56s with 35s is said to be perfect for the '12 auto. Sure, if you have 4.10s now you're probably fine but if you don't and you're going to re-gear then you may as well go for the 4.56s.

 

That's good to know! Thanks I'm feeling a little better now I was anxious at first. But I got some heavy bumpers and a lift so hopefully the 4.88 will even out!