Regear with 38s

Brian

Jeep Fanatic
Y’all, before you blow a gasket over this gearing thing there are a few facts you need to know.

Kid will be living in south Alabama (flat).

Home will be 5 hours north (still flat)

Off road use will be limited for a quite a few years as he will be focusing on college, being a collegiate athlete and med school.

BFG KO2 37s are more like large 35s.

He’ll be fine on the 4.56 gears until he is employed and can make this jeep a dedicated trail rig.
My only point in this is that you're wasting $1,500

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Pthorpe84

Moderator
Staff member
I will throw this out there. If anything. Switch to 4:88 gears. No reason to go to 4:56. Waste of money. If you are going to down gear that much, I will trade you my 4:10 and you will get the same results. Or at least not enough to tell.




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SSinGA

Jeep Fanatic
Appreciate the input y’all but it’s getting 4.56 gears in it. I’ll be sure to let you know what the outcome is once it’s done.
 

Brian

Jeep Fanatic
Appreciate the input y’all but it’s getting 4.56 gears in it. I’ll be sure to let you know what the outcome is once it’s done.
No one here wants to change your mind. We are just trying to help others not make the same mistake you are. [emoji3]

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SSinGA

Jeep Fanatic
No one here wants to change your mind. We are just trying to help others not make the same mistake you are. [emoji3]

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Mistake is a relative term. You can’t make an across the board recommendation that all Jeeps with 37s need 5.13 gears.

If we lived in a western mountain state my decision would probably be different. If there were plans to wheel it hard my decision would probably be different.

I took all the usage considerations into account before ordering the gears. All the charts only provide starting points and not a hard “if you have 37s you must have this gear ratio”.

As stated before, I’ll post up the results once we get them swapped. If I think it was a mistake for our situation I won’t be afraid to say so.
 

Brian

Jeep Fanatic
Mistake is a relative term. You can’t make an across the board recommendation that all Jeeps with 37s need 5.13 gears.

If we lived in a western mountain state my decision would probably be different. If there were plans to wheel it hard my decision would probably be different.

I took all the usage considerations into account before ordering the gears. All the charts only provide starting points and not a hard “if you have 37s you must have this gear ratio”.

As stated before, I’ll post up the results once we get them swapped. If I think it was a mistake for our situation I won’t be afraid to say so.
How did this turn out? We just put 5.13's in the Travis Mills Foundation Jeep for use with 37's. Still building so I cannot tell you how they are on the road.
 

SSinGA

Jeep Fanatic
How did this turn out? We just put 5.13's in the Travis Mills Foundation Jeep for use with 37's. Still building so I cannot tell you how they are on the road.
The 4.56 has been perfect for our build. I could see wanting the 5.13 if it was a dedicated trail rig and you might want 40s at some time.
 

Ryno1035

Jeep Newb
13 jkur auto. I want 38s and have beat my head against the wall researching gear/tire combo. The go to is 35 with 4.56 and 37 with 4.88 but the stamp on the side of the tire is always wrong. I believe 38s are actually closer to 37 inches. Because of this I’m planning 4.88. It’ll be a dd
 

The NotARubicon

Jeep Owner
13 jkur auto. I want 38s and have beat my head against the wall researching gear/tire combo. The go to is 35 with 4.56 and 37 with 4.88 but the stamp on the side of the tire is always wrong. I believe 38s are actually closer to 37 inches. Because of this I’m planning 4.88. It’ll be a dd
If you plan to do hard-core rock-crawling, the lower the better.. if you also have a stick, you can't go low enough..
I have a stick/manual trans and went to 4.88 when i got my 35's.. rock crawling was tough, but not too bad.. a few weeks ago i went to 37's and now i hate my life and wish i had gone to at least 5.13 ..or 5.38 ...
 

whataboutbob

Jeep Newb
I am trying to decide on gearing and am finding some information that doesn't seem to match up. SSinGA said his son is running close to 3K rpm at 70mph with an AT and BFG 37's (really 35.6") but the above gearing chart shows he would be running closer to 2400 RPM while a manual trans would be close to 3k? I have a manual trans with 37 BFG's and waffling between 4.56, 4.88, and 5.13. I have 3.21's now and this morning was running just under 1500 RPM at what I believed was close to 70mph based on typical traffic speed. That seems to align with the automatic chart? Any help would be greatly appreciated.
 
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