Re-gearing an Auto JK - 4.88's vs 5.13's?

    I'm looking to re-gear my 2011 JKU Rubicon Auto that has 35's with stock 4.10's gears now. I'm on the fence about what gear to go with. A lot of people on the web push for the 5.13's but they all seem to live out west where there are more hills and average highway speeds are around 65 mph. I was leaning more towards 4.88's since our average speeds are closer to 75 mph and we don't have the hills they do. I made the mistake of over gearing my TJ and having to redo it after the fact. So this time I'm trying to get as much information as possible. I'm looking for a good combination that will give me the right RPM's on the highway so that my transmission isn't always jumping out of O/D all the time. At the same time some more power when needed wouldn't be such a bad thing. Of course the other question is whether I'm going to move up to 37's in the future.


    Please let me know what you guys are running and whether you are happy with your setup.

    The math told me to go with 4.88's but all the posts on the web told me to go with 5.13's or even 5.38's.


    I am SO glad I went with 5.13's in my JKU auto with 35's. It makes all the difference on the highway and still needs to downshift at 80 MPH going into hills.


    The only draw back is strength of the smaller pinion. Otherwise, 5.13's are a no brainer for an Unlimited auto with the 3.8L engine.

    I've got a similar question as the op but its just the JK and not a JKU. Does the same hold true or is there a difference b/c of the wheel base, etc.? Sorry to hijack the thread....just seems like the more information we can all get the better.

    &quot;Always do sober what you said you&#039;d do drunk. That will teach you to keep your mouth shut.&quot;--Ernest Hemingway<br /><br />&quot;Only dull people are brilliant at breakfast.&quot; ---Oscar Wilde

    I'm running 5.13's with 35'' tires and a 6 speed manual in my JK. My RPM's run a little on the high side right now but my tires are a non-aggresive A/T. I plan on moving up to 37's GoodYear MT/R's so it should balance out a little more once I do.

    I am pretty happy with the 5.13's but if I were staying with the same tire and given mine is manual I would have went with 4.88's

    Just my .02 to help you make your decision.

    Quote from Grunt2213


    I've got a similar question as the op but its just the JK and not a JKU. Does the same hold true or is there a difference b/c of the wheel base, etc.? Sorry to hijack the thread....just seems like the more information we can all get the better.


    The difference would be the weight of a 2 door vs a 4 door. The 2 door auto can take 4.88's/35's better than the 4 door from what I can tell.



    Yeah, you mentioned going to 37's when you were regearing. I think you'll be happy you did it right the first time so you are set for 37's. The 3.8 V6 likes to rev more than the 4.0 I6.

    What about a 2012 JK with the new 3.6L. I have 34s right now but the next set will be 35s. The stock 3.21 gears are less than spectacular. My 12 JK with 34s and a 3" lift and 3.21 gears still feel better than my 08 JKU with the 3.8L and 3.73 gears. Im thinking with the 3.6L and the 5 speed auto I can get away with 4.10 or 4.88s. what do you think?

    3.73s are great with the 32" BFG MTs on my Rubi. So, going from there, 4.56 should be more than enough for 35s (you know you're either gonna get 35s or 37s the next time you get tires!)

    Jerry / Whatevah

    2020 Gladiator Mojave - 33" Falken mud tires, LoD side steps, Zroadz bed rack, Quadratec QRC winch bumper, Superwinch EPi 9.0, Kleinn on-board air, Kleinn air horns, lots of lights, Yaesu ham radio with GPS tracker.

    Gone- 2012 JK Rubicon with stuff. Long gone- Long-arm 2001 Cherokee with stuff.

    Quote from whatevah


    3.73s are great with the 32" BFG MTs on my Rubi. So, going from there, 4.56 should be more than enough for 35s (you know you're either gonna get 35s or 37s the next time you get tires!)


    The fact that Jeep switched the stock Rubi from 4.10's to 3.73's in the 2012 says a lot about that engine/tranny combo. I have a feeling it has as much to do with the new 6 speed auto as the engine but the higher HP, higher torque 3.6 definitely is a factor.


    (I still want to drag race you Jerry.) :innocent:

    You can still get the 4.10 gears, but they're optional now. I stayed with 3.73 because I didn't intend on getting bigger tires right off the bat.

    Jerry / Whatevah

    2020 Gladiator Mojave - 33" Falken mud tires, LoD side steps, Zroadz bed rack, Quadratec QRC winch bumper, Superwinch EPi 9.0, Kleinn on-board air, Kleinn air horns, lots of lights, Yaesu ham radio with GPS tracker.

    Gone- 2012 JK Rubicon with stuff. Long gone- Long-arm 2001 Cherokee with stuff.

    Quote from KnoxRents


    The fact that Jeep switched the stock Rubi from 4.10's to 3.73's in the 2012 says a lot about that engine/tranny combo. I have a feeling it has as much to do with the new 6 speed auto as the engine but the higher HP, higher torque 3.6 definitely is a factor.


    (I still want to drag race you Jerry.) :innocent:



    I want in on that drag race! although I think I would lose unless we were on route 1

    Quote from BlueLesPaul2006



    I wonder what my tires on your rubi with the 3.73s would feel like. I can see an experiment happening for that.


    Hmm I wonder if they'll fit without rubbing. We can try it one day and see what happens.

    Jerry / Whatevah

    2020 Gladiator Mojave - 33" Falken mud tires, LoD side steps, Zroadz bed rack, Quadratec QRC winch bumper, Superwinch EPi 9.0, Kleinn on-board air, Kleinn air horns, lots of lights, Yaesu ham radio with GPS tracker.

    Gone- 2012 JK Rubicon with stuff. Long gone- Long-arm 2001 Cherokee with stuff.

    Quote from whatevah


    Hmm I wonder if they'll fit without rubbing. We can try it one day and see what happens.



    That was my thought. I think you would be fine with no rubbing issues. The wheels are backspaced enough that turning is ok. However if you are flexing the suspension you will rub. But I think to drive around town for a test it would be just fine. they are wider than your stock tires but they are only like 1.5 inch taller.

    Thank you - I actually got in touch with Brian from holly oak 4x4 and he is going to do them for me. He did the gears in my other jeep and did a great job then. As a bonus he gave me a great price. I will let you know how everything turns out.

    So if I wanted to take my 11 JK on the trails should I go to the 4.88 or the 5.13? Im running stock gears and 35s and have stayed away from anything taxing as I fear breaking a gear right now. Just trying to get my thoughts together on this so I can start saving.


    Sent from my DROID RAZR using Tapatalk 2

    &quot;Always do sober what you said you&#039;d do drunk. That will teach you to keep your mouth shut.&quot;--Ernest Hemingway<br /><br />&quot;Only dull people are brilliant at breakfast.&quot; ---Oscar Wilde

    Quote from Grunt2213


    So if I wanted to take my 11 JK on the trails should I go to the 4.88 or the 5.13? Im running stock gears and 35s and have stayed away from anything taxing as I fear breaking a gear right now. Just trying to get my thoughts together on this so I can start saving.


    Sent from my DROID RAZR using Tapatalk 2


    Are you running a manual or auto transmission?

    Auto


    Sent from my DROID RAZR using Tapatalk 2

    &quot;Always do sober what you said you&#039;d do drunk. That will teach you to keep your mouth shut.&quot;--Ernest Hemingway<br /><br />&quot;Only dull people are brilliant at breakfast.&quot; ---Oscar Wilde

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