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Old 07-23-2013, 03:06 PM   #1
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4.88 or 5.13 for 37" tires in 2013 Rubicon Auto

I'm really torn on what gears to put in my 2013 JK Rubicon Unlimited w/ Auto transmission w/ 37" tires. It a work in progress and I should have the tires by next week, but unsure of the gears. I look at the charts and have spoke with many people. Some say 4.88 & others say 5.13. I live in rural PA and have a 14 mile commute to work. I'm close to Rausch Creek and plan to spend a good amount of time there. Due to the cost, I only want to gear once. Can anyone help offer advice with supporting data? Thanks!!

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Old 07-23-2013, 03:18 PM   #2
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5.13s

4.88 if you plan on... not carrying the spare, using aluminum bumpers, never carry anything on the back or passengers, or not having any armor or skid plates.

But then again, I like having a responsive vehicle, that will accelerate accordingly if I need to do an in-a-hurry maneuver regardless of what I have on the car bwehehehe. Plus the extra torque available when offroading helps.

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Old 07-23-2013, 03:31 PM   #3
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I went with 4.56 on my 2013 w/ auto and 37 in tires. Works great for me. Right in the middle since I DD a lot
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Old 07-23-2013, 09:51 PM   #4
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Quote:
Originally Posted by lovey74 View Post
I'm really torn on what gears to put in my 2013 JK Rubicon Unlimited w/ Auto transmission w/ 37" tires. It a work in progress and I should have the tires by next week, but unsure of the gears. I look at the charts and have spoke with many people. Some say 4.88 & others say 5.13. I live in rural PA and have a 14 mile commute to work. I'm close to Rausch Creek and plan to spend a good amount of time there. Due to the cost, I only want to gear once. Can anyone help offer advice with supporting data? Thanks!!
If you have to use it for a daily freeway commute, then I think 4.88 would be the way to go. Assuming you have the auto tranny, you will be doing freeway speeds around 2500-3000 rpm or so. if you go 5.13 I think you will be more like 3500. (don't quote me on that, those are rough estimates). Otherwise 5.13 would be the way to go. It's really just the freeway driving that sucks with extreme gearing.

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5.13s

4.88 if you plan on... not carrying the spare, using aluminum bumpers, never carry anything on the back or passengers, or not having any armor or skid plates.

But then again, I like having a responsive vehicle, that will accelerate accordingly if I need to do an in-a-hurry maneuver regardless of what I have on the car bwehehehe. Plus the extra torque available when offroading helps.
Although that may be true for the old V6 with the 4 speed auto, I think with the pentastar, and either the 6 speed manual, or 5 speed auto, it isn't as big of a deal.
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Old 07-23-2013, 10:37 PM   #5
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I went 4.88 for my manual. At first I felt like I had gone too far but after a couple months of driving it I'm very very glad I went 4.88. My initial shock was I felt like I was doing a lot of gear rowing but it is now second nature. I think if I had gone less I'd be very unhappy. I even think I could have lived with 5.13 in a manual now that I'm so used to the 4.88.

For my 2cents with an auto, not having to row the gears, I would go 5.13 and not look back.
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Old 07-23-2013, 11:31 PM   #6
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I've got 37s on my '12 Rubicon with Auto and I run 5.13s. Works really well. I haven't tried 4.88, but super happy with what I've got.
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Old 07-24-2013, 11:44 AM   #7
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If you have to use it for a daily freeway commute, then I think 4.88 would be the way to go. Assuming you have the auto tranny, you will be doing freeway speeds around 2500-3000 rpm or so. if you go 5.13 I think you will be more like 3500.
3500 is an exaggeration... A customer has 37s on a 2012 manual with both aftermarket steel bumpers and does roughly 2700~2800 at ~70mph. I dont think the autos have that much increased gearing compared to manuals to fly up to 3500 O_o unless freeway speeds include 90mph.

You may do 3500 with stock tires at standard highway speeds, however.
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Old 07-24-2013, 08:41 PM   #8
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3500 is an exaggeration... A customer has 37s on a 2012 manual with both aftermarket steel bumpers and does roughly 2700~2800 at ~70mph. I dont think the autos have that much increased gearing compared to manuals to fly up to 3500 O_o unless freeway speeds include 90mph.

You may do 3500 with stock tires at standard highway speeds, however.
Dude c'mon man, literally directly after you ended that quote at that period, I said "(don't quote me on that, those are rough estimates)". I get it man, my point was just to be careful with extreme low gearing for highway speeds. I have a 2012 5 speed auto with 35s and 4.56 gearing and I do 2500rpm at 65mph.
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Old 07-24-2013, 08:47 PM   #9
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Are the 4.10 gears in the rubicon that bad with 37's? I've spoke with several people that are happy with the 4.10's and 37's on the 3.6 automatic??

What is the rpm difference between 4.10 and 4.88 gears?
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Old 07-24-2013, 08:55 PM   #10
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I can't imagine anything less than 4.88 with 37's. Since you don't have much of a commute, I'd go with the 5.13 personally.
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Old 07-26-2013, 10:25 AM   #11
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Thanks for the input everyone! After absorbing everyone's replies (thank you) & studying the 2012 3.6 gear chart I have decided to go with 5.13's. it will be another month until I have them in, but will keep all of you posted on what I think! I will also post pics of build after my Poison Spyder fenders, bumpers, rock sliders are powder coated & installed.
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Old 07-26-2013, 11:52 AM   #12
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I'd say 4.56's....
But if you are carrying lots of extra weight (armor), have heavy wheels, won't do a lot of highway miles, and live in a hilly area, go more aggressive.
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Old 07-26-2013, 12:14 PM   #13
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Thanks for the input everyone! After absorbing everyone's replies (thank you) & studying the 2012 3.6 gear chart I have decided to go with 5.13's. it will be another month until I have them in, but will keep all of you posted on what I think! I will also post pics of build after my Poison Spyder fenders, bumpers, rock sliders are powder coated & installed.
Sounds like an awesome Jeep in the making! LOVE my PSC stuff. Can't wait to get 37's one day!
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Old 08-01-2013, 12:59 PM   #14
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Sounds like an awesome Jeep in the making! LOVE my PSC stuff. Can't wait to get 37's one day!
Thanks! Its getting there....
Have the 3" Teraflex with 8 control arms added, Fuel 17x9 wheels, 37x12.50x17 Toyo Mud Terrains, Teraflex HD front and rear sway bars, Teraflex Rear Tire Carrier. Today most of the Poison Spyder Items Arrive....Yay!!!
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Old 08-01-2013, 01:21 PM   #15
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My vote would have to go with 4.88's. I think 5.13's would be to high for the 37's. We have a HEAVY 2013 JKU running 5.13's on HEAVY 40's.

If you would like to talk more about it, feel free to PM or email us my friend!

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Old 08-01-2013, 02:04 PM   #16
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My vote would have to go with 4.88's. I think 5.13's would be to high for the 37's. We have a HEAVY 2013 JKU running 5.13's on HEAVY 40's.

If you would like to talk more about it, feel free to PM or email us my friend!

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I agree with this guy. I have the same engine and 37's with heavy slabs, heavy armor and skids, and about 200lbs of tools and fluids. 5:13's will be screaming on the highway. I'm normally right around 3000rpm at 75-77mph with 4:88's.
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Old 08-01-2013, 02:09 PM   #17
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Russ, see we are about that same deal with our 40's and SpyderLocks. Each one of our wheels and tires are about 150lbs. My vote is 4.88's.

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Old 08-01-2013, 04:15 PM   #18
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I'm with Jason, 4.88's. I have the auto and 3.73 gears, I run 2k rpm at70 mph and get 20 mpg. I can tell it's slower than stock but not by tons. I will be going with possibly 4.88's because we are in the mountains here. If I was still in MD or some where flat I'd stick with the 4.10's or maybe go 4.56's. Not only are smaller gears more economical for gas, too small and it will cost more gas, but the larger you go the smaller the pinion gets meaning the weaker it gets. Climbing Parley's pass here in Utah, one of the more severe, I can hit it at 3k RPM in 3rd gear an stay at 70mph or accelerate if need be.
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Old 08-01-2013, 04:47 PM   #19
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Running 37s in my JKUR and have it stock at 4:10's for now. Honestly, drive it for a month and see if you'll even care afterwards. I ran it for a couple of months without a spare and didn't even see the need to regear. Now I'm running with a heavy spare and at first I wanted to regear, but I'm still holding off on it for now. I'd go to 4:88 if I do end up doing it but 4:10 have been just fine thus far.
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Old 08-01-2013, 04:54 PM   #20
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I'm with Jason, 4.88's. I have the auto and 3.73 gears, I run 2k rpm at70 mph and get 20 mpg. I can tell it's slower than stock but not by tons. I will be going with possibly 4.88's because we are in the mountains here. If I was still in MD or some where flat I'd stick with the 4.10's or maybe go 4.56's. Not only are smaller gears more economical for gas, too small and it will cost more gas, but the larger you go the smaller the pinion gets meaning the weaker it gets. Climbing Parley's pass here in Utah, one of the more severe, I can hit it at 3k RPM in 3rd gear an stay at 70mph or accelerate if need be.
you guys and your fancy pentastar engine! i'm running 37s and 4.88s (3.8L - auto) in the 10,000' peaks of florida... honestly no way i'd be happy with a 4.56... part of me wishes i went 5.13s yes my gas mileage sucks... i get like 14 something around town... if i do a full tank on the highway and keep it around 2000 rpm i can get around the low 16s... in a convoy i do better...

but the power is not always there.. definitely better than the 3.73s that's for sure...
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Old 08-01-2013, 04:56 PM   #21
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4.88 should be good to go on a '13 auto for 37's

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Old 08-01-2013, 04:56 PM   #22
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Running 37s in my JKUR and have it stock at 4:10's for now. Honestly, drive it for a month and see if you'll even care afterwards. I ran it for a couple of months without a spare and didn't even see the need to regear. Now I'm running with a heavy spare and at first I wanted to regear, but I'm still holding off on it for now. I'd go to 4:88 if I do end up doing it but 4:10 have been just fine thus far.
Great advice on waiting it out....
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Old 08-01-2013, 06:09 PM   #23
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Yeah the pentastar and 5 speed trans is a whole new ball game when it comes to gearing. My wife's 3.8 had 5.13's in MD and it was fine but with the altitude and thin air the 5.38's would be nice but I'm not going to regear, I do my own gear work.
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Old 10-06-2013, 12:55 PM   #24
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I went with the 5.13's with the Penistar & auto and couldn't be happier. Its running maybe 200-300 rpm more at 70 mph when compared to the 4.10's. I have all the pick-up I need and in 4 low can easily crawl up on very large rocks. Glad I didn't go with the 4.88's or 4.56's.
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Old 10-06-2013, 01:00 PM   #25
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'12 AUTO ON 37'S. 4.88's are good. 5.13's would have been a bit better but i drive alot of miles. if u want max performance go 5.13's, if yah want performance and good drivability for long trips, commuting etc go 4.88

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