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-   -   2012 Rubi build...37's with 5.13 or 5.38 gears?? (https://www.jk-forum.com/forums/modified-jk-tech-2/2012-rubi-build-37s-5-13-5-38-gears-233222/)

JKLarson 05-23-2012 08:32 AM

2012 Rubi build...37's with 5.13 or 5.38 gears??
 
Hey guys, just picked up a new 2012 rubi...love it! :rock:

Planning out my build and I think I am going with a 4" TeraFlex (not sure if LA or SA yet...) and 37's...

Stock Dana 44's front and back with 4.10 gears...should I go with 5.13 or 5.38 gears?? The 3.6 engine is awesome so far...I live in Colorado and it will be a DD and a trail beast. Will 5.38 be too much?

I have an auto tranny...

Thanks in advance...

mattgt5 05-23-2012 09:09 AM

I have a 12 rubi with 4.10 auto and 35s. I would not change gears. Plenty of power and get around 18 mpg on my daily commute. I am going to 37 soon and have no plans to regear

JKLarson 05-23-2012 09:29 AM

What kind of elevations do you go through? Living in Denver and heading up to the trails in the mountains is a hike...5,000 feet to 11,000+ feet...I am worried about those long runs uphill with 4.10's

arjeeper 05-23-2012 09:33 AM

I think with the pentastar we have to set some of the past gearing suggestions aside. I also wonder if either of the options you're suggesting are too much. What about 4.56s?

JKLarson 05-23-2012 09:46 AM


Originally Posted by arjeeper (Post 3030832)
I think with the pentastar we have to set some of the past gearing suggestions aside. I also wonder if either of the options you're suggesting are too much. What about 4.56s?

You make a great point, this is a totally different engine with a lot more power...I based my gear calculations on "old school" rule of thumb. I looked at some online calculators and it says jumping from a 32" (stock) to a 37" tire a 4.88 would bring it back close to stock...

Any Colorado guys out there have the pentastar and did some gear changes?

ranjr 05-24-2012 02:12 PM

Unless you want to climb the hills in OD, 5.13s & 5.38s are too much for 37s. I too have 35s and 4.10s and still find myself with the ECO light on all the time. I'd look at 4.56 or 4.88s.

TeraFlex 05-24-2012 02:58 PM

Running 37's with 5:38's in mine. Makes it nice on climbing up hills, lots of bottom end. However not the best for mpg's, I'd consider 4:88's -5:13's. However there is no way I would ever change mine down.

ornjeep 05-24-2012 04:01 PM

I'm in Colorado with 37s an went with 4.88. It feels pretty much the same as stock. Cruises E470 at 80-85 and gets up the mountains well. I don't have any complaints with the setup. I'd agree that the pre2012 recommendations don't apply to the 12s.

JKLarson 05-24-2012 05:06 PM


Originally Posted by ornjeep
I'm in Colorado with 37s an went with 4.88. It feels pretty much the same as stock. Cruises E470 at 80-85 and gets up the mountains well. I don't have any complaints with the setup. I'd agree that the pre2012 recommendations don't apply to the 12s.

Thanks dude, I appreciate it. How big is your lift and what kind?

ornjeep 05-24-2012 05:26 PM

4 1/2 AEV. So far I'm loving it.


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