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I am looking for advice on which way to go with my gear upgrade. First off, a little back ground...

The vehicle is a 2011 JKU Rubicon with an automatic transmission. Currently it is 100% stock. I have just purchased a 3.5 Clayton Premium Lift for the Jeep. I am looking to install the lift and the tires as soon as I acquire the tires. Hopefully this will be within the next two weeks. I am also currently debating out MTRs w/ Kevlar and BFG KM2s, however I am very much leaning towards the KM2s, as for everything I am reading leads me to believe they are a better for my particular needs and I have had a few sets of the KMs in the past. The tires are going on the OEM wheels, with the addition of wheel spacers.

Now the big debate comes in when we start talking gears. The last Jeep I had was a TJ Rubicon and the 4.10s did just fine with 33" tires IMO. The JK, in my opinion, is already a little underpowered from the factory. I know that throwing the 37s on the stock axles with 4.10s is going to suck! I don't plan on leaving it that way very long (2-3 weeks at the most.) My plans for the Rubi consist of some light to moderate wheelin', but it will spend the majority of its life on the road, taking me to and from whatever adventures I may undertake.

So, for those of you who have knowledge, and particuarly those who have ran 37s and re-geared, what are your thoughts on the subject. More importantly, why do you think that way?

I appreciate any constructive input I can get on this, as I am looking to you guys to be one of my primary sources of education on the matter.

TIA

Bill

nthinuf

5.38's...

joe002

I’m running 5.38s with 35s in a 2 door and am happy, so I would think you would want 5.38s with 37s and a 4 door.

My setup is better than stock in accelerating and much better off-road (primarily crawling for me). My gas mileage is about the same as my stock mileage.

See my experience here: https://www.jk-forum.com/forums/show...-35s-and-5.38s

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Any personal experience? I am looking for performance comparison between the two, how it is comparted to stock? MPG info would be great too!

YingYang

I have 3.5" lift, 37's, auto and I regeared to 5.13's. Mine is the X so thats as far as I could go. I dont know how the 5.38's feel but here is a little info on mine.

RPM's @ 70mph = 23-2400
Mpg's = 13 ish

Its was still dragging going up steep inclines on the highway, shifting constantly. If I had the option I would go with the 5.38's.

I had 2 choices, new front axle and gear that to 5.38 along with another regear of the rear. Or, RIPP supercharger. They were both on my mod list but I went with the RIPP first and now the 5.13's are not a problem anymore.

Just my

Here is the best gear/tire calculator I have seen. Spot on or dang near it.
https://www.jk-forum.com/forums/show...tio-Calculator

nthinuf

Here is the 'other' Auto JK gearing thread from today. And there is a link in it to yet another Auto JK gearing thread. Plenty of info and charts to help with the decision.

https://www.jk-forum.com/forums/show...-5.13-or-stock

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Thanks. I was looking at that as well.