3.8 auto w/5.13 gears on 37" tires

Clark Collins

Clark Collins

New member
My 2010 JKU sport auto with Rubi axles has 5.13 gears and I'm currently running 35" tires. I have the 3" EVO plush ride lift and chopped fenders so have room to go with 37" tires I think. I am in the process of doing a rear bumper delete and installing a rugged ridge tire carrier that will enable me to carry a 37" spare. This gearing with 35" tires seems ideal to me, so I would like to hear from forum members running 37s with the same set up that I have. I'm concerned that the larger tires might change the gearing enough to make the OD unusable. The gearing chart shows only about a 130rpm drop, but shows it going from "acceptable" to "minimum allowable" gearing. I would like to hear some real world experiences with this change including how the stock rubi axles hold up as well as drivability.
 
RockinAZJK

RockinAZJK

Caught the Bug
As far as I know most on here with 37's and the 3.8 are running 5:13. Personally that is what I'll be going with. Those running 4.88 that I personally know actually wish they had 5.13. And 5.38 (correct me if I'm wrong) break a hell of a lot easier or are too small


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tdougherty81

tdougherty81

New member
Clark Collins said:
My 2010 JKU sport auto with Rubi axles has 5.13 gears and I'm currently running 35" tires. I have the 3" EVO plush ride lift and chopped fenders so have room to go with 37" tires I think. I am in the process of doing a rear bumper delete and installing a rugged ridge tire carrier that will enable me to carry a 37" spare. This gearing with 35" tires seems ideal to me, so I would like to hear from forum members running 37s with the same set up that I have. I'm concerned that the larger tires might change the gearing enough to make the OD unusable. The gearing chart shows only about a 130rpm drop, but shows it going from "acceptable" to "minimum allowable" gearing. I would like to hear some real world experiences with this change including how the stock rubi axles hold up as well as drivability.
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I had 37s on my 08 with 5.13s and EVO 3" Plush Rides. I didn't have the Rubicon but I did have the Rock Jock 44 up front. As far as gearing goes 5.13s was not bad on 37s but compared to my new jeep with the 3.6 and 4.10s it was sluggish. OD was minimal.
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