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Discussion Starter · #1 ·
I've read the gearing charts but I'm looking for some real world experience advice.

I have a manual 6 speed, 2013 JK (2 door) which has the 3.6 Pentastar. Currently I'm running 315/70/17 tires which measure out to about 34 inches. My 4.56 gears seem a little low for this setup at 70mph but off road it seems pretty good.

I'm thinking of going with 37" tires once my front prorock is installed.

I need some real world experience about how 4.56 gearing works city / highway / trails / rocks.

Right not I have the 2.72 TC but will be swapping in a 4:1 (I'm sure that will help a lot for off road and rocks).

Thanks for any input!


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I have 4.88 and 35s with a manual so not a direct comparison. I would think you need a little more gear for 37s but I would wait until the 37s are installed before deciding how much more to go, if any. You may like what you end up with, especially if you think you got a little too much gear now at 70mph. Oops, edit, your putting a pro rock in. If you want to go 37s get them first and see how you like it with your existing setup
 

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If you DD it, you would probably be better off with 4.88s for 37s. If it is a weekend warrior and you are more worried about off road, you would be better off with 5.13s. 4.56 is undergeared for 37s either way.
 

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If you DD it, you would probably be better off with 4.88s for 37s. If it is a weekend warrior and you are more worried about off road, you would be better off with 5.13s. 4.56 is undergeared for 37s either way.
but...but...but... if 3.21s are good for 35s then certainly 4.56s would be good up to AT LEAST 42s????

:pullinghair:
 

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Discussion Starter · #5 ·


So from what I'm gathering, most with world experience are saying this chart is wrong when it says 4.56 and 37" tires is "acceptable" for on road use?

I do daily drive it and it has to be able to go the speed limit on highways without running at high RPM. I know I'm sacrificing some off road performance by having the ratio higher but that's why I was hoping to make up for that by going lower in the TC.

Guess I'll have to just wait and see... might be re-gearing again. Lol


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It'd be OK if you live close to sea level and don't drive in hilly areas all the time. If you figure that a 37" tire has a weighted rolling diameter of 35.5", you'll be around 2400rpm at 70mph. That's OK if you're making sea level power.

Mark

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4.88 and don't look back!

I have the 3.6, 6-speed manual and 4.56. Running 315/70/17. For me it's great because I'm right at 2500 rpm at 70 in 6th. Loving that I get 18.5 mpg highway. BUT---I'm still downshifting to 5th on most hills, even easy grades.

The only reason that I didn't go 4.88 is because the manual trans in 2012+ has a 1st gear ratio that is 20% lower that 1st gear in the automatic. My crawl ratio at 4.56 is actually better than my buddy's 4.88s in his auto. And I'm killing him at the pump.

I do plan on 37's in a few years but will also have swapped in a 4:1 tcase by then.
 

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Discussion Starter · #8 ·
4.88 and don't look back!

I have the 3.6, 6-speed manual and 4.56. Running 315/70/17. For me it's great because I'm right at 2500 rpm at 70 in 6th. Loving that I get 18.5 mpg highway. BUT---I'm still downshifting to 5th on most hills, even easy grades.

The only reason that I didn't go 4.88 is because the manual trans in 2012+ has a 1st gear ratio that is 20% lower that 1st gear in the automatic. My crawl ratio at 4.56 is actually better than my buddy's 4.88s in his auto. And I'm killing him at the pump.

I do plan on 37's in a few years but will also have swapped in a 4:1 tcase by then.


This is good information. Thank you for sharing. It would suck to have to pay for another re-gear but I originally didn't have plans to ever do 37s... so 4.56 seemed like the logical choice. I should've known better. Lol


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4.88 isn't going to make that much more difference than 4.56. If I already had the 4.56 I would definetley try it out on a 2 door before I dropped the coin. If I wanted to make a difference I would jump to 5.13
 

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Discussion Starter · #11 ·
4.88 isn't going to make that much more difference than 4.56. If I already had the 4.56 I would definetley try it out on a 2 door before I dropped the coin. If I wanted to make a difference I would jump to 5.13

Thanks for the reply.

Yes, I will definitely see how it does before I drop the coin but was trying to put my mind at ease by getting some perspective of those that potentially had 37s with 4.56.

I think it'll be pretty fair on road, here in central PA, probably have to down shift for some hills.

Off road will probably not be as good, but I'm banking on going lower in the TC to make up for it.




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