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Unread 09-14-2013, 09:24 AM   #31
HOKIES2010
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I ran heavy 37s with 4.10s for acouple months down in flat FL. It was doable but not fun. I think 35s would doable as well but also not fun.

I run 5.13s now with the 37s. Pairs well with the manual and 3.8.

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Unread 09-14-2013, 12:40 PM   #32
HappyTrails
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Quote:
Originally Posted by HOKIES2010 View Post
I ran heavy 37s with 4.10s for acouple months down in flat FL. It was doable but not fun. I think 35s would doable as well but also not fun.

I run 5.13s now with the 37s. Pairs well with the manual and 3.8.
I remember running my 37's with 4.10's for a short while in the hills around NW Georgia. All I remember thinking was, "Thank God for the supercharger! This think would be absolutely unbearable." Then I put 5.38's in it and am back to being a happy camper.
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Unread 09-14-2013, 05:21 PM   #33
jenniferjeep
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So this got me thinking what does regearing to lower gears do to your gas milage? I would think that it is going to drop.
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Unread 09-14-2013, 06:14 PM   #34
JIMBOX
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If you regear to one of the better ratios (5.13/5.38) your gas mileage drops drastically---at first, because it's like you gotta engine transplant (almost), but

As soon as you get over the new toy, mileage gets better-

I was able to get high 18 mpg driving 60 mph and the avg mileage driving at 70 is 16.2 and towing 14.9-

However my JKUR weighs over 2-3/4 tons when ready for a trip-so the lighter and more economically driven can show great benefits in gas mileage--

This is only for 07 to 11 JK/JKUs--because you're putting the 3.8l v6 in its happy comfort zone-- 2200/2400 rpm--

Of course, everyones different and the tire size is instrumental in these figures-

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Unread 09-14-2013, 06:59 PM   #35
SLADE
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Quote:
Originally Posted by jenniferjeep View Post
So this got me thinking what does regearing to lower gears do to your gas milage? I would think that it is going to drop.


Not if you increase your tire size at the same time. Lower (numerically higher) gears can improve your fuel mileage when your running a tire that is too tall for your gear ratio. Larger tires make fewer revolution per mile so in turn it takes fewer revolution of the axle shaft to put the motor in it's RPM range for a given speed. The numerically higher gears also adds a mechanical advantage to help turn the taller and heavier tires.


Your average speed is also a factor on the fuel mileage for a given ratio. Most gear charts have are based on going around 70 MPH. If the average speed of your typical commute is only 45mph -60mph, you can run a numerically higher gear than the chart recommends and still maintain your fuel economy.

It has less to do with the number and more to do with matching the gear ratio, tire size, and speed to a given motors efficient RPM/power range.
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