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Are you re-gearing for 35s or 37s?

Are you re-gearing for larger tires?


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vavaroutsos

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That would be much appreciated. To be honest, I'm more concerned with the MPG (I know, I know, its a jeep) and drive at expressway speeds as that is where most of my driving happens. I also want to create as less stress as possible on the other components due to the larger tires. I've been leaning towards 4.88 but I honestly don't have any basis for that except that seems to be a very common answer from others.
Here you go. Be sure to use the dynamic tire diameter if you want accurate results. You can usually determine this from the revs/mile specified by the tire manufacturer (at least for their given conditions).
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MojitoJLUR

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Here you go. Be sure to use the dynamic tire diameter if you want accurate results. You can usually determine this from the revs/mile specified by the tire manufacturer (at least for their given conditions).
It seems like there is about ~100 rpm difference between 4.88 and 5.13 holding everything else constant for 37s.
 

vavaroutsos

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It seems like there is about ~100 rpm difference between 4.88 and 5.13 holding everything else constant for 37s.
At 65 mph, that's about right. At higher speeds there will be more difference, and at lower speeds there will be less difference.
 

jimlove9771

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Is anybody re-gearing for 35s?

What about 37s?

(If yes, what are you re-gearing to?)
I have a JL 2 door Sport S. Put on BFG 35 K02’s with Mopar 2” lift. Here’s the kicker. I have the first in the world installation of Prodigy Performances Stage 2 Turbo Kit for the JL. Ken of Prodigy (designer of the turbo kit and chief engineer) is flying to Houston tomorrow to personally oversee the final tuning of my Jeep. I still have the stock 3.45 gearing on my 8 speed auto. We intend to discuss with him whether I would benefit substantially by regearing and if so what ratio would be the best. For those of you are not familiar this turbo kit it will supposedly inceprease my RWHP from stock of 247 to 401!! (Note: 285 at the crank to about 440). Stay tuned as I will inform you of the results. I also intend to have my build Dyno tested just to know exactly my Jeep’s power and torque.
 

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JLscorpio31

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So it seems like the overwhelming majority of those going up to 35s are not gear swapping. Why is that? Feel it’s not needed or is it a matter of the cost of the gear swap? I’ll be buying a JLUR and likely going with 35” tires. I’d planned on gearing to 4.56 to restore lost torque and acceleration. Is this not common (new to Jeeps, not gear swaps)?
with the JKU it was more common, with the new 8 speed(auto) there's no need to re-gear on 35s especially on Rubis, hell you can do 37s. I have a Sahara and will be installing 35s on rancho 2" sport lift. I suppose it's all about preference.
 

UKCATS

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I just put 35’s on my 2 door Rubicon. I might be able to live without re-gearing, but, the transmission isn’t utilizing 7th and 8th as well as stock. Yes I have used a Tazer to reset for tire size.
 

BLLFRG

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After reading the 6 pages of responses.... I am left with more questions than answers.

I think the problem comes from not asking/answering the primary question "What are you trying to do with your Jeep?" I am not a rock crawler. I love the trails, dunes and baja type of off roading. So I would think that I would want better highway/acceleration consideration when looking at regearing....assuming 37's on a JLR. With the mention of weight change per tire, accessories, etc etc.... Then would I want to be in the higher area (lower numerical gearing)? Example 4.88 instead of 5.13? Or vise versa? Needing the lower torque to move the greater mass, yet maintain the momentum with less stress....it would seem to me that 4.56 isn't a big enough jump from the 4.10 should I run 37x13.5/18 at 125Lbs per tire (x5 with the spare), after market bumper, winch, etc etc etc.....

Again, not rock crawling so slow in low isn't what I am targeting. Daily driving so smooth at 70MPH and trail riding is the purpose....so am I just all flubbed up or does that sound about right?
 

vavaroutsos

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After reading the 6 pages of responses.... I am left with more questions than answers.

I think the problem comes from not asking/answering the primary question "What are you trying to do with your Jeep?" I am not a rock crawler. I love the trails, dunes and baja type of off roading. So I would think that I would want better highway/acceleration consideration when looking at regearing....assuming 37's on a JLR. With the mention of weight change per tire, accessories, etc etc.... Then would I want to be in the higher area (lower numerical gearing)? Example 4.88 instead of 5.13? Or vise versa? Needing the lower torque to move the greater mass, yet maintain the momentum with less stress....it would seem to me that 4.56 isn't a big enough jump from the 4.10 should I run 37x13.5/18 at 125Lbs per tire (x5 with the spare), after market bumper, winch, etc etc etc.....

Again, not rock crawling so slow in low isn't what I am targeting. Daily driving so smooth at 70MPH and trail riding is the purpose....so am I just all flubbed up or does that sound about right?
In order to get more torque at the rear wheels (all else the same), you need a numerically higher gear ratio. More torque (higher gear ratio) also means more acceleration as well as higher RPM for a given speed (all else the same). This is the same direction you would go for crawling. The only difference I see between crawling and dunes is you probably want more HP for the dunes since you want speed. But if you're not planning an LS swap or something, put in numerically higher gears (I would go 5.13 for 37" tires) and see how you like it. The 3.6L likes to rev anyhow.
 

JC7

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Weird. I'm running 38s on my JLUR with an automatic and don't have any real issues. I will be swapping out the 4.10s for 5.13s. I don't know anyone with a Rubicon on 35s with either transmission complaining.
Have you gone 5.13 yet?
 

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chevymitchell

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Are you installing them? If not, what are you getting charged to have it done?
I’m installing them.

I’d expect 400-600 per axle or 5-7 hours of labor per axle if I were paying someone to do it.
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