When we bought our 2012 Jeep JK Wrangler, we had always planned to upgrade it’s axles to a set of Dynatrac ProRock 60’s. Of course, being that money doesn’t grow on trees, we decided to use the time until we could afford the upgrade to extensively test just how well a set of 37″ tires would do with the new 3.6L Pentastar motor running factory 4.10 gears. For almost 2 years, we took our Jeep just about everywhere we could, driving it to and from the trail, on the highway and around town, up and over mountains, hard and fast through the Mojave Desert, up and over steep ledges in Moab and, crawling it over big rocks on trails like the Rubicon. And, after racking up over 45,000 miles on the odometer, what I can tell you is this… it can be done and it does work surprisingly, okay. For someone who’s never driven a re-geared equivalent, they may not even know what they’re missing.
Having said all that, recent circumstances forced us to upgrade our front axle sooner than we had planned for and, while we were at it, decided to just bite the bullet, take advantage of Off Road Evolution’s $999 special and have our Jeep re-geared with a set of 5.13’s at the same time. After testing them out extensively on the 2013 JK-Experience, all I can say is – why in the hell didn’t we do this sooner!!
While the 3.6L motor has a good amount of power and will do a decent job of compensating for larger tires, it simply can’t make up enough of a difference especially in situations like on long or steep hill climbs. Here, your transmission will try to help make up the difference by dropping gears and running your RPM’s up close to 6 grand just to keep you moving. Of course, this will cause your engine and transmission to run really hot and in some cases, cause your Jeep to go into limp mode – ask me how I know. With a set of 5.13’s, this will no longer be an issue as you’ll have plenty of power to do the same job in a higher gear and running at a lower RPM. Of course, this is to say nothing about the fact that on the rocks, a set of 5.13’s will also significantly improve your crawl ratio – running 37″ tires on 4:10 gears, you’ll go from a 3.36:1 to a full 4.21:1! Of course, for those would might complain about the increase in RPM at highway speeds, what I can tell you is that it’s really insignificant. In fact, the difference you’ll see when compared to a stock Rubicon running 32″ tires and 4.10 gears is only about 200 RPM as you can see in the calculators below:
Trust me, if you’re planning on running 35″, 37″ or bigger tires on your 2012-Up JK, you really will be doing yourself a BIG favor to get it re-geared at the same time. If you live in the SoCal area, be sure to take advantage of Off Road Evolutions $999 special too as it really is a deal that is hard to beat.
You have convinced me! did you see any improvement in mpgs after the regear?
I am assuming you are running a 6 spd? I have 4.10s and an Auto on my 2012 with 35s and its perfect. Call me crazy but I think 2865 RPMs on road trips is too much for too long.
Brad, around town, yes. There is less effort needed to get you going. On the highway, we’re now pushing a bit more RPM higher at highway speeds so no.
ray, I am running an auto. 35’s and 4.10’s is a good combination. We are running 37’s.
I was curious if you had done any kind of upgrades to the rubicon axles like c gussets or truss’ or anything of that sort? Also did you break anything, or have to replace anything due to premature failure?
We are running a Dynatrac ProRock 44. I personally wouldn’t waste any money beefing up a factory Rubicon front axle as it’s really just a Dana 30 with 44 center section. If anything, upgrade your shafts to chromoly with full circle clips and maybe gussets but that’s about it.
Need some advice please: My budget won’t allow the re-gear on my 2012 Auto with 3.73’s for another 6 months. I want to go straight to 37’s, MC 3.5 lift, cut my fenders, strengthen the front axle (C gussets and sleeves), but my regear needs to wait. Is that do-able without any hardcore offroading and Arizona flat roads?
Eddie: You have had extensive experience with the 3.8 and now the 3.6 Jeeps. I have a 2010 JKUx with the auto and 3.73 gears on 33s. I’ve been thinking about possibly regearing for 35s and adding lockers or possibly upgrading to a new Rubi. If I got the Rubi I would not want to have to regear for 35s for primarily overlanding type use, but some intermediate rock crawling. It is also my daily driver, but I don’t have a commute as I’m retired. What are your thoughts comparing a regeared 3.8 to a 3.6 Rubi?
If it were me, I would get a new Rubi with a 3.6L motor. It really is that much better of a motor. However, if money is an issue, regearing your 2010 to 4.88 will help bring your performance back to about stock with a set of 35’s. 5.13’s will give you a boost in power but will leave your dana 30 pinion very small and a weak point.
Hi, I have a 2013 JKU Sahara with 3.21 ratio. 3.5 rock krawler lift TN front and rear drive shaft and OMEmu steering… I been running 35’s on 18″wheels for over a year without problem but I just recently bought a rear 44 arb air locker …. Now my friends are telling me I need go regear both front and rear also due to the “max tow” option (although I don’t have it) the front differential needs to be changed completely for regear other wise it will blow…. Any thoughts on the regear ? If so what ratio? 3.73?4.10? It’s also my DD… 🙂
I just bought a 2012 JK w 35’s 3.5 lift but i’m guessing stock gears. need advice on which way to go with gearing for street and mud use more than climbing .. my question is can I get by with axel sleves and upgraded axels .and locker on my dana 30 to suit my needs and rely on the 30 … plus upgrading rear 44 as well ?
Is it safe to assume you don’t have a Rubicon with 4.10 gears? If you do, you should be fine. If not, I might recommend 4.88 gears. 4.56 will bring you back up to stock but 4.88 will give you just a bit more power. No need for sleeves, just gussets.
When you ran the stock setup with the 37s for nearly two years, did you make any drive shaft modifications?
Yes, I upgraded my shafts to a set of JE Reel 1350’s. However, you can get by with just upgrading your front shaft and running a factory rear so long as you have a 4-door.
What’s up project jk! I just got a 2 dr 2007 jk. Automatic Trans with 33’s on it. I’m looking to get 35’s and regear. I’m seing a lot of people talking about auto gears and manual gears. Is a 4.10 or 4.56 different on a automatic then a manual? If so what would you recommend I regear to. I’ve got stock axles, rear is a d44 and front a d30. Jeep x. Non rubicon. From what I’ve seen, around town and daily driving is pretty good with a 4.56 and 35″ combo.
I have a 2013 jku 3.6 non-rubicon 6spd manual 3.21 gears on 35s. Also have winch bumpers sliders to add some weight. I am ready to buy some gears.. I’ve been sitting on the money because I can’t make mind up. I’ve been told by people that know jeeps that 4.10 would be perfect. Others tell me if you’re going to spend the money go 4.56. Also I drive highway speeds 80% of the time @ 70mph. I hit the trails any chance I get. I’m not sure if running the jku 2500 rpm all the time is a good idea… Your opinion?
i have a 2014 JK Sahara with a 4″ lift and 35″ tires. Reading through the site it sounds like I need a new fron drive shaft and gears. I dont have any power issues and I dont want to get worse gas mileage. extreme terrain has an add that recommends 5.13 gears. What doyou think? And what axle should I purchase? Thanks
I drive ’12JKUR auto 4.10 gears with 3.5″ X factor Rock Krawler lift and 1″ body,Front Recon King 2.0 coil overs, front and rear 1350 JE Reel drive shafts, c gussets. Order 17×8.5 -6 Fuel trophies with 35×12.50Rx17 NItto terra grapplers M/T. I really want to order 37″ but am worried about the wear and tear on the motor and gears and axles. It is a daily driver in the flat roads of Amarillo TX, but take trips to Moab and Colorado to rock climb. Its only $250 to go up to 37s. Advise would be greatly appreciated!
I’m in the process of putting 488 gears in my 99 TJ Wrangler. 4″ lift – 35 12.5 15 tires – 4.0 5 speed
with a Sprintex Supercharger. I can’t wait to see the performance with 488’s installed. My mpg at the present time is right around 10 but don’t really care, I’m looking for speed, sound, and performance.
I just bought a 2015 Jk wrangler. I’m going to the transition to make into a rock crawler. When I purchased this jeep sport I compared it to a rubicon. The price for a rubi was to much for me. I was thinking why pay extra just for leather seats. Well now that I have my jeep I realized what lockers are and was not on this model. Any way I’m going to do a suspension lift on 37. My question is what gear ratio you recommend and when I decide later to get lockers do I need to re gear again? Also what suspension you recommend?
I saw this post, and found it helpful. I did a lot of research and it seems to me that i’ve found many different opinions.
I own a 2012 2 door sport on a 3.5″ lift w/ 37’s on it. I do minimal off-roading, With that being said, I like to push it. I Live in Los Angles, California and as you would know we have a lot of highways and I do a lot of highway driving.. What would your opinion be on gear ratio for my condition? I’ve heard 4.10s to 4.56 to 4.88 and of course 5.13s.
Thanks !
Hey everyone, question for you. My wife has a 2013 JKU with 3.21 gears. I recently installed a 3.5″ with some 35″ mud terrains. She’s been using her Jeep to trailer her horse around to ride local trails and it’s always been a challenge with her gear ratio. Now that I’ve put the lift and tires on, I told her not to tow the horse until we re-gear. According to the charts I’ve seen, it says we COULD do 4.88’s instead of 4.56 but the guys at our local 4 Wheel Parts said absolutely not and to go 4.56 at most. They were both running 37’s on their rigs with 4.56 gears. What do you think? 4.88 is in the green on the chart I was looking at.
Ryan McBride
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I have the same issue as Keving, did not see an answer:
I have a 2013 jku 3.6 non-rubicon 6spd manual 3.21 gears on 35s. Also have winch bumpers sliders to add some weight. I am ready to buy some gears.. I’ve been sitting on the money because I can’t make mind up. I’ve been told by people that know jeeps that 4.10 would be perfect. Others tell me if you’re going to spend the money go 4.56. Also I drive highway speeds 80% of the time @ 70mph. I hit the trails any chance I get. I’m not sure if running the jku 2500 rpm all the time is a good idea… Your opinion?
Hello, I’ve got a 2012 rubicon 4.5″ Terra flex lift running nitro mud grapplers 37×13.50R20 JKS and curry correct steering. Stock drive shafts… Issues with the drive shafts I wanna install a Terra flex Slip Yoke Eliminater, add Beefy front and rear drift shafts and ReGear it. Please help me which the best options for this. Money isn’t an issue my poor jeep clunking is. I’ve only got 21k miles on it and already issues from not re gearing. Thank you
Ok,I bought my 2014 jkurx in 2014,I ordered it from the dealership when I saw the 2013 limited edition which then for 2014 was called the x and 2015 was called the Hard Rock. I basically ordered this 4 door Rubicon with everything except the color matching hard top and fenders.I got the upgraded tow package and upgraded the 4.10 gears for front and back that cost extra and was by far not cheap either. This Rubicon has Dana 44 both front and rear and as Im reading, as Im understanding and correct me if Im wrong, If I wanted to lift it and put 37s on it Id have to regear? Now Ive heard that yes you can get away with 35s but 37s I need to regear? Thats like 2000.00 right there alone!! Im curious , does anyone know how the 2017 recon is set up gear wise? I know it comes with 35s stock on Dana 44s but is it still using 4.10 gears? If I would have gotten better advice before I ordered I would have been better off not getting the upgraded 4.10 gears and kept with the 3.73 gears, it would seem Id be paying twice for this mistake, any comments would be appreciated.