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Discussion Starter · #1 ·
I know, I know and I'm sorry but it's such a huge mod and very important to get right the first time. That is why I must ask a specific question before I proceed with the surgery. I've been doing research for months and feel I have a good handle on everything gears. Yet here I am starting a new thread but only interested in opinions from those in a similar situation with the same (or close to) setup as me. I am 99% sure that upgrading from 3.21 to 4.56 is the right choice for me. However, what I would like to know is if there is anybody out there that has regretted going with 4.56 and wished they had done 4.10 instead???

Background:

2013 2dr sport 3.6L automatic
2.5" lift
315/70/17 duratracs - small and light 35s (33.5 actual)
Stock bumpers, no winch and soft top so very, very light jk
Don't tow
About 10k miles on 3.21 (not as bad as I thought it would be but time to upgrade now that I can afford it)

Mainly concerned with DD including town/country roads, city streets, and about 20% highway...extended highway driving happens about once a month (not much). I offroad when I can but most of my wheeling is just snow covered back roads and trails, nothing extreme and no rock crawling. I don't live at elevation but the terrain is hilly and not flat by any means. I would also like to point out that I am willing to trade mpg for a more enjoyable driving experience.

Like I said, only looking for real world experience from peeps with a rig like mine that can answer this specific question. 4dr owners, those with a manual transmission, and the real jeepers that spend more time in 4L than 2H don't have to reply....unless you want to of course (more info that can help others is always positive). So is there anyone out there in my shoes that regeared to 4.56 and said "Damn that's too low, should've done 4.10!"?

p.s. Thanks to the WF community for providing a wealth of knowledge on this subject. ..I ALMOST didn't have to start another thread. Also, thanks to a few of you that I sent PMs to...all thoughtful responses that I'm grateful for. And Derf, your gear ratio calculator is the shit!
 

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Discussion Starter · #3 ·
About 70...only go above that if in a big hurry.
Won't go any bigger but maybe a true 35 when my duras wear out.
Aftermarket bumpers and winch possibly down the road but not anytime soon
 

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About 70...only go above that if in a big hurry.
Won't go any bigger but maybe a true 35 when my duras wear out.
Aftermarket bumpers and winch possibly down the road but not anytime soon
only true 35s are 37s lol...all 35s end up 33-34 mounted
 

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Discussion Starter · #5 ·
only true 35s are 37s lol...all 35s end up 33-34 mounted
Yeah I'm noticing a trend there lol. Glad I didn't let anyone talk me out of "35s" when i bought these 315s. Had I went with 33s they'd be closer to stock 32s....hence buyer's remorse.
 

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I would do at least 4.56... And consider 4.88. I have a 13 auto with true 35s (37 bfg ko2. Also light) and I like the 4.88s but would even consider 5.13 if I did it again. I think 4.88s and 35s would be perfect but 4.56s would also be a good fit, especially if you don't wheel much and do a bit of highway.
 

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Discussion Starter · #7 ·
I would do at least 4.56... And consider 4.88. I have a 13 auto with true 35s (37 bfg ko2. Also light) and I like the 4.88s but would even consider 5.13 if I did it again. I think 4.88s and 35s would be perfect but 4.56s would also be a good fit, especially if you don't wheel much and do a bit of highway.
Thanks.
Haven't even considered 4.88 with an auto. With those ko2s & 4.88 you have, does it feel close to stock for on road performance or better/worse? You rockin a 2dr or 4dr?
 

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Thanks.
Haven't even considered 4.88 with an auto. With those ko2s & 4.88 you have, does it feel close to stock for on road performance or better/worse? You rockin a 2dr or 4dr?
whoops, sorry, i have a 4 door. Just re read your post and saw that you were looking for feedback from 2 dr owners.

I have the rk x factor 2.5 lift, flat fenders, no spare tire, no hardtop (trektop pro), crawler conceptz skinny front and rear bumpers with a warn m8000. The jeep accelerates and passes as if it still had its baby shoes on it. It gets onto rocks a couple times a month and i'm happy with the gears but i def do not feel the gears are too low, by any means
 

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If you have 3.21 with stock 32s, you are undergeared to begin with. Even 4.10 would be a dramatic improvement. For the uses you describe, I think 4.56 would be your best option. It will seem like night and day compared to your current stock setup. Now you turn about 1959rpm at 70. With 4.56 and 35s, you will be at 2500-2600rpm (depending how close to true size the tires are).

I run about 2700-2800rpm with 37s and 5.13. I geared my Jeep to crawl the big rocks tho. I would love 5.38 on the trail, but that would be too low on the street since my rig is still a daily driver. For a Rock Crawler on 35s, I would go 4.88. But that's not what you plan to do so 4.56 should be cool.

My Jeep is a two door Rubicon.
 

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Target green area here for a mostly pavement/mild trail rig.
 

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Discussion Starter · #11 ·
whoops, sorry, i have a 4 door. Just re read your post and saw that you were looking for feedback from 2 dr owners.

I have the rk x factor 2.5 lift, flat fenders, no spare tire, no hardtop (trektop pro), crawler conceptz skinny front and rear bumpers with a warn m8000. The jeep accelerates and passes as if it still had its baby shoes on it. It gets onto rocks a couple times a month and i'm happy with the gears but i def do not feel the gears are too low, by any means
Thats exactly what I want. Started out with the 16" steelies, then 32" sahara take offs, then 315 duratracs and can't help but remember what it felt like with the dinky little 29s...so I'm looking to get that same performance back with the larger tires (or better).

Sounds like you got a nice setup there vdog. I'm thinking 4.56 will be about prefect for me.
 

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Discussion Starter · #12 ·
If you have 3.21 with stock 32s, you are undergeared to begin with. Even 4.10 would be a dramatic improvement. For the uses you describe, I think 4.56 would be your best option. It will seem like night and day compared to your current stock setup. Now you turn about 1959rpm at 70. With 4.56 and 35s, you will be at 2500-2600rpm (depending how close to true size the tires are).

I run about 2700-2800rpm with 37s and 5.13. I geared my Jeep to crawl the big rocks tho. I would love 5.38 on the trail, but that would be too low on the street since my rig is still a daily driver. For a Rock Crawler on 35s, I would go 4.88. But that's not what you plan to do so 4.56 should be cool.

My Jeep is a two door Rubicon.
Yup i figured with my true tire size I should be about 2700 at 70 and still have a little room to go faster before reaching 3k when I need to...from my experience 3k rpms is where my engine feels like it's unhappy. I recently test drove a rubicon with 4.10s on stock tires and took it on the highway...was well out of the green and gotta say it felt great and totally sold me on 4.56. Problem is the only automatic I could find was a 4dr with a hardtop...quite a bit heavier than mine. Just how much does weight factor into the equation? Are the charts pretty accurate regardless of weight? Would there even be a substantial difference in rpms between JKs and JKUs?
 
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