Gear ratios for 37" and 3.8l auto

SierraSilver

SierraSilver

New member
Does anybody have experiences on different options when running 37" tires? I have a Sahara with replaced Dana 44 axles with the e lockers, and stock 4:10 ratios, and a super chip programmer. I will be welding gussets and additional steel to my C's and tubes. Should I be concerned with power, mileage, or strength with running 37"? I also have cold air and performance exhaust, but after reading a couple write ups with the 3.6l, I'm a little concerned with upgrading from my current 33.3" Nittos to 37. Thanks for any help.


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5.13's would be your best bet for 37's with the 3.8. i currently run them with 35's bacause i know evenually i will go to 37's
 
I run 5.13's, which is the highest you can go in a Dana 30. with 35" Nitto Mud Grapplers. Plan on going to 37's next. I hear guys with 44 can go to a 5.38's. Might be worth doing for extra power.
 
Nick Unlimited said:
I run 5.13's, which is the highest you can go in a Dana 30. with 35" Nitto Mud Grapplers. Plan on going to 37's next. I hear guys with 44 can go to a 5.38's. Might be worth doing for extra power.
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I run 5.38's in mine and like them a lot. Ran them with 35's for about a year before I went to 37's and they wee fine as well, IMO.
 
If you have a auto and front and rear 44's I would do 5:38's.
I wish I had more go with 37's and 5:38's. I even ran 5:38's in my Dana 30 for awhile. ( Richmond made a batch for the JK Dana 30 at one point.)
 
SierraSilver said:
Does anybody have experiences on different options when running 37" tires? I have a Sahara with replaced Dana 44 axles with the e lockers, and stock 4:10 ratios, and a super chip programmer. I will be welding gussets and additional steel to my C's and tubes. Should I be concerned with power, mileage, or strength with running 37"? I also have cold air and performance exhaust, but after reading a couple write ups with the 3.6l, I'm a little concerned with upgrading from my current 33.3" Nittos to 37. Thanks for any help.


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Click to expand...

I have 5.13's with D44's on 37's and they are great. 3.8L. Power is fine and I have the Flashpaq with 87 octane tune. I average 14.9mpg on day to day driving but when I hit the highway for long trips it goes up to about 19mpg. No complaints here.
 
Thanks for the info. Americas tire is advising me against changing unless I regear. I might be stuck at 35" for now .


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cozdude said:
5.13's would be your best bet for 37's with the 3.8. i currently run them with 35's bacause i know evenually i will go to 37's
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This....^^^ also only thing I noticed going from 35 to 37s w 5.13 s the while time was a decreasing in braking. If u r gonna do 35s by any chance maybe consider 488

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I run 513s and love em but I don't "daily drive" mine

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I'm running 5.13 in my '07 JKU with 35" BFGs. I have a flashpaq and have adjusted my speedo for tire size which helps with performance. I would have gone to 5.38 but was given a lot of advice from this forum (and other jeep forums) that it's not a good idea due to pinion size becoming very small and weak point. I bought a used rubi rear axle that already had 5.13s in it and just regeared the front axle. The 5.13s are a huge improvement in power vs. the 4.10s I had especially when driving higher altitudes and steep inclines like New Mexico and southern Colorado have. I think 5.38 would be better for 37s but just keep in mind the pinion issue.
 
I installed 5.13 gears in mine over a year ago with stock 3.8L, Dana 30/44 combo and 35" trail grapplers and seemed like a perfect combo.

Then I went to 37" trail grapplers and it seemed a bit under powered to me but I am still very happy with the setup (I do daily drive mine when needed).

When I went to 37's, I sleeved and gusseted my 30 and have had great luck with the setup on and offroad. I assume a flashpaq or some kind of tuner would help as well.
 
Don't mean to hijack but I didn't wanna start a new thread for what's probably a simple question but how do I find out what gear ratio I currently have? I'm asking because I got in an accident years ago and insurance replaced the rear housing and insides. However, I had a 2 wheel drive x (most basic model they made) with the stock housing (which I wanna say is a D30. The thing looked like a toothpick) but when they replaced it they put on a 44 (if it wasnt a 44 already) and I don't know what's in there. I want to regear but I'm just curious to know what's in there now

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