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Old 06-02-2014, 02:02 PM   #1
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Re-gear 2011 Rubicon Unlimited for bigger tires?

Hi. Just bought a 2011 Unlimited with stock Rubicon 17" wheels, 32" tires, and 4.10 gears. I'm swapping these for 16" wheels and 35's on my Wrangler. Wondering how much difference re-gearing would make? I've seen this before as a guide to get as close to factory setting as possible:

Old Gear Ratio × New Tire Size ÷ Old Tire Size = New Gear Ratio....so:
4.10 x 35 / 31.6 = 4.54 which mean 4.56 new gears.

Is the performance difference enough to pay over $1000 to go from 4.10 to 4.56? Should I consider 4.88 or 5.13? What would those do for me?

Not my daily driver, but will be driving it several times per week, mostly highway.

Trying to figure out my cost/benefit so your advice is greatly appreciated. Thanks.

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Old 06-02-2014, 02:39 PM   #2
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Quote:
Originally Posted by jamalcal View Post
Hi. Just bought a 2011 Unlimited with stock Rubicon 17" wheels, 32" tires, and 4.10 gears. I'm swapping these for 16" wheels and 35's on my Wrangler. Wondering how much difference re-gearing would make? I've seen this before as a guide to get as close to factory setting as possible:

Old Gear Ratio × New Tire Size ÷ Old Tire Size = New Gear Ratio....so:
4.10 x 35 / 31.6 = 4.54 which mean 4.56 new gears.

Is the performance difference enough to pay over $1000 to go from 4.10 to 4.56? Should I consider 4.88 or 5.13? What would those do for me?

Not my daily driver, but will be driving it several times per week, mostly highway.

Trying to figure out my cost/benefit so your advice is greatly appreciated. Thanks.
I think the best thing to do for you would be to put the new tires on it and drive it. At first you may notice the performance drop a lot, give it a few days. As long as you are happy with how it drives, there is no reason to regear it. If you're not able to stay in high gear on the highway or if you're generally unhappy with the new "sluggish" feeling, then get it regeared. You'll make the final decision based on what you want out of the Jeep!

I should have asked, is it an automatic? If so, you'll need a Superchips Flashcal or the like to get the shift points in check. That'll help the feel a lot.

Let me know what questions you have!

-Ryan

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Old 06-02-2014, 03:03 PM   #3
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Check out the gear chart for the 3.8L engine and pick your desired cruising engine RPM. The higher numerically (shorter gears) the higher the RPM and performance, and lower fuel economy. The gear charts have color coded bands for performance and fuel economy.

I would run at least 4.88 with 35" particularly because it's not your daily driver, but that is really a personal preference. Swapping gears is pricey so err on the side of performance for off roading. If you read some of the older threads for the 3.8, you will find that 5.13 gears are a popular choice with 35s. You have more flexibility with a manual because you can control shift points but you may limit your use of top gears.
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Old 06-02-2014, 03:57 PM   #4
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Great advice. It is an automatic. I may have made a mistake in my calculation which might change your recommendation. The new tires are 315-75/16 which actually makes them 37's if my math is right. Using the same gear formula:

4.10 x 37.7 / 31.6 = 4.89 which is very close to what you recommended and on the way to 5.13.

Any idea what would be a good price for parts and labor? I live in Dallas, and there's a 4 Wheel Parts and several good off-road shops.
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Old 06-02-2014, 04:20 PM   #5
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Originally Posted by spinlock View Post
Check out the gear chart for the 3.8L engine and pick your desired cruising engine RPM. The higher numerically (shorter gears) the higher the RPM and performance, and lower fuel economy. The gear charts have color coded bands for performance and fuel economy.

I would run at least 4.88 with 35" particularly because it's not your daily driver, but that is really a personal preference. Swapping gears is pricey so err on the side of performance for off roading. If you read some of the older threads for the 3.8, you will find that 5.13 gears are a popular choice with 35s. You have more flexibility with a manual because you can control shift points but you may limit your use of top gears.
Thanks. Where do I find this gear chart?
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Old 06-02-2014, 05:05 PM   #6
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315s are actually considered a 35.
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Old 06-04-2014, 03:19 PM   #7
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With your 4:1 transfer case you are geared ok for off road use. It is the top gear that is geared too high for street use with the 3.8 and auto transmission (assuming you have the auto transmission). I've run 5.38s with 35s before, and liked that combination. The overdrive on that transmission is so deep that you cant gear it too low, they don't make gears that low. I would recommend at least 5.13s. Don't waste your time with 4.56s.
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Old 06-04-2014, 04:04 PM   #8
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Originally Posted by jamalcal View Post
Great advice. It is an automatic. I may have made a mistake in my calculation which might change your recommendation. The new tires are 315-75/16 which actually makes them 37's if my math is right. Using the same gear formula:

4.10 x 37.7 / 31.6 = 4.89 which is very close to what you recommended and on the way to 5.13.

Any idea what would be a good price for parts and labor? I live in Dallas, and there's a 4 Wheel Parts and several good off-road shops.
Your math isn't right. 315/75R16 tires are 35's. They usually measure out to 34.x and when you have weight on them they can dip a little shorter, into the 33's.

The equation is ((section width/25.4) * aspect ratio / 50) + wheel height = diameter. So ((315/25.4) * 75 / 50) + 16 = 34.60

As far as which gears to get:

Going from 4.10 to 4.56 is a waste of money. That small of a change is not enough to notice. If you're going to change gears, you want to go up to 4.88 or 5.13. The JKU is a heavy vehicle, the 35" tires are wider and heavier, and the 3.8 V6 lacks low end torque. As far as I can remember, most people who regear for 35's on a JKU go with 4.88 if not 5.13. That gets the engine RPMs up to where they need to be to make the engine perform in it's happy spot and give you good all around performance. The Rubicon can take 5.38 gears (the other Wranglers can't go that deep because the gears are not available for the Dana 30 in the front). That may be a little too much for 35's on a daily driver but maybe not.

As far as where to go in DFW:

I used to live in Fort Worth and I always had good luck with 4 Wheel Parts. I'm sure they haven't been perfect every time but they run a lot of 4x4's through their shops every day so they have to be doing something right.
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Old 06-04-2014, 05:03 PM   #9
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Super helpful. Thanks.
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Old 06-04-2014, 10:36 PM   #10
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I run 4.88's and 33's in my 10 auto and i love the pep compared to the stock 3.73. i honestly couldnt believe the difference it made
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Old 06-11-2014, 05:15 PM   #11
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On Saturday, I'm putting 3" lift on back and 3+1 on the front. Decided on 5.13 gears, and can hardly wait...4.10 stock gears are way more sluggish than I expected.

Question is do old 4.10 gears have value on ebay or craigslist, or could my son use them on his 2004 TJ (doubtful). Thoughts?
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Old 06-11-2014, 06:34 PM   #12
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Originally Posted by jamalcal View Post
On Saturday, I'm putting 3" lift on back and 3+1 on the front. Decided on 5.13 gears, and can hardly wait...4.10 stock gears are way more sluggish than I expected.

Question is do old 4.10 gears have value on ebay or craigslist, or could my son use them on his 2004 TJ (doubtful). Thoughts?
The gears are not the same between the JK axles and any other Dana30/44. Apparently someone has made some kind of conversion kit that lets you use JK gears in an older generation Dana 44 but I don't know much about those. I know you have to clearance the housing somewhat.

A lot of people don't like to install used gears so the market it slim. But you may be able to sell the gears to someone. It wouldn't hurt to list them and see what kind of offers you get.
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Old 06-13-2014, 11:11 AM   #13
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Wonder if my old Rubicon Unlimited shocks can be pulled off when new lift/shocks installed, and be used short term on my son's 2004 TJ? Recently bought the TJ and still checking it out mechanically, and want to make sure we decide to keep it before investing in new lift/shocks. But it needs shocks badly now, so thought the Rubicon shocks might work short term. Thoughts?
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Old 06-13-2014, 03:11 PM   #14
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I had a friend that put new Rubicon shocks on his YJ, and they worked great. I would suspect they would work on a TJ as well.

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