37s on 3.8 - JKowners.com : Jeep Wrangler JK Forum
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post #1 of 11 Old 03-01-2018, 08:51 PM Thread Starter
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37s on 3.8

Tossing around the idea of putting 37s on my 08 jku but talked to a local shop and he was saying how with 37s and 5.13 I really wouldn’t be able to run down the interstate. Is this true? My Jeep is my DD and I would like to make frequent trips to Colorado for wheeling as I live in Nebraska. For those running 37s on your 3.8, which gears do you have and can you run 75mph under or around 2500 rpm? Any input is greatly appreciated!
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post #2 of 11 Old 03-02-2018, 03:34 AM
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Noaho25,
I have an 08' jk with a slush box, Gears are 5.38 and run 37"x13.5 Toyo
and have zero problems running 75 MPH all day long, for the last 4 years.
I go over Snoqualmie Pass in Washington all winter long. Just my .02 cents
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post #3 of 11 Old 03-02-2018, 04:29 AM
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Been running 5.38's with 37's in my 09 for about 6 yrs with no issues. Run down the interstate at 70-75MPH with no issues.
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post #4 of 11 Old 03-02-2018, 04:49 AM
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my 3.8l four door has 5.13s and an auto running 37s . On 2nd set and have no issues. I can even beat the other two in an interstate race because mine will go 80mph with no issues . One finger driving.
It takes some diligence, understanding, work & many considerations but is totally doable. Just make sure your axlehousings are up to the task. Hitting holes with super heavy tires when driving at high speed is a great bender of parts & things. Artec is a very good vendor to bookmark.




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post #5 of 11 Old 03-02-2018, 05:02 AM Thread Starter
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I know this can be kind of a redundant questions for lifted Jeeps but it still is a factor, what are you getting for mpg?
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post #6 of 11 Old 03-02-2018, 09:05 AM
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ya know, I have no idea. I am not a good candidate to ask that question for many reasons.




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post #7 of 11 Old 03-02-2018, 05:26 PM
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Ran 37's for a long time (60k miles). 5.13 gears and auto. Averaged 14 mpg, and travel the interstate all the time. (70 mph) FWIW - I still have the original d30 front axle with no issues, even when I go mudding.

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post #8 of 11 Old 03-05-2018, 05:41 AM
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Ran 37's with 4.10's for about 2 years when it was my DD. Then I upgraded to 5.13's and ran them as a DD for 2 years. Now the jeep is 99% trail use only but it still does 75mph down the highway to get there. I have no idea on MPG nor do I care, its a jeep.
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post #9 of 11 Old 03-05-2018, 07:14 AM
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i drove 160 miles round trip yesterday to my home OHV Park & kept track for OP;
at 70-80mph on freeway with many long, straight inclines ( Cumberland Ridge - google it or ‘ Nashville Dome’ ) , running 25psi in brand new 37” MTs on a 3.8l with auto and 5.13 gears plus a FlashPaq set to account for the changes , the MPG reading from evic was 14.8mpg averaged .


(note: your mileage may vary)


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post #10 of 11 Old 03-07-2018, 05:03 PM
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Not accounting for OD, but a decent comparison for tire sizes Vs gears...


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post #11 of 11 Old 03-07-2018, 06:09 PM
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I’ve ran 37s and 5.13s on my 07 since May 2010. Wish I’d have put 5.38s in.
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