Comments on running 37s on Rubicon Extreme with 456 gears

Trident1231

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35’s to 37’s is a very small change. The final drive ratio will be almost equal to a stock rubicon with 4.10’s and 33’s. Approximately 1950rpm at 70 mph. As far as handling, assuming the same tire is used, will be a negligible difference. Even off road the difference isn’t huge, unless you are going with a more aggressive tire. If you are stepping up from the KO2 to a hybrid tire or full mud terrain then the off road difference will be huge. We road trip our JLUR all over on a 37” extreme terrain, and my wife daily drives it, but it’s not for everyone. They are a little louder on the street, wet traction suffers a little, I hear traction in ice is really bad (not an issue in CA) but in the mud, deep snow, soft sand, loose dirt, etc any mt will be vastly superior to the KO2.
I'd have to disagree about the ko2s, I'm running 37s ko2s, on snow and they are very very very good. Muds plain suck on snow , not enough sipping in the tires.

 

Rodeoflyer

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IMO, I don't think it's going to be worth re-gearing if you have 4.56's from the factory. The 8 speed auto is just too damn good. You will be permanently fine at 4.56's, even on a heavy 37.
I agree, with the auto 4.56 will be fine. If you plan to go larger than 37's it will be an issue, but even then at altitudes above 10k feet. My little 3.6 was wheezing up above 10k and you need gears to offset that.
 

Dudley Dawson

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I think AEV uses 4.56 gears on all of their JL370 builds (running 37” K02 or KM3). Seems it would be ok. I’m still 4.10 on 35s no issues at all (of course now I want 37s 🙃)
 

guarnibl

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I agree, with the auto 4.56 will be fine. If you plan to go larger than 37's it will be an issue, but even then at altitudes above 10k feet. My little 3.6 was wheezing up above 10k and you need gears to offset that.
Yeah just depends on the weight really, once you get to 40”+ absolutely.
 

Zandcwhite

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I'd have to disagree about the ko2s, I'm running 37s ko2s, on snow and they are very very very good. Muds plain suck on snow , not enough sipping in the tires.
You are saying snow, but describing ice. That’s exactly why I said deep snow. Sipping is great for ice or a few inches of snow (especially with ice underneath) but doesn’t do anything in deep snow. In my experience deep snow, sand, mud all benefit from bigger lugs and deeper voids of a mud terrain For the same reason, self clearing.

 

Mac Haik CDJR Georgetown
 
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