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Old 02-26-2009, 07:31 PM   #1
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regearing for 31s?

I have 31in MT mtz. My stock gearing is 3.73 (tag on the diff said so).

Jeep has 30,000 miles and its a 03. When driving in town it just feels sluggish. The tranny feels sloppy. well, more of the shifting.

When driving on the hwy I cant put it into overdrive. If I do and I have cruise on it downshifts alot.

It gets 11-13 mpg never seen 14mpg.

My only mods are 31in tires on stock wheels.
Air-raid intake.
and BB lift.

I was told that regearing would help with most said above. But how much w ould it help going from 3.73 to 4.11?

Any other ideas would be great.

I know that the jeep is a brick and is not supposed to get good mpg. But I know it should be better than this.

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Old 02-26-2009, 07:50 PM   #2
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3.73's and 31's should not really be an issue, some down shifting perhaps on hills etc. I ran 33's with 3.73, and it was fine to me. As for the MPG, did you change the speedo gear to get the correct reading.. if not you MPG will be off.

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Old 02-26-2009, 07:51 PM   #3
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I ran 31's w/ 3.55's for two years and never had a problem. I am about 14-15 mpg. Are you sure you need to regear?
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Old 02-26-2009, 07:52 PM   #4
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I dont know. If thats what I need to do.

thats why I am asking.
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Old 02-26-2009, 07:53 PM   #5
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No I didnt change the speedo gear.
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Old 02-26-2009, 07:56 PM   #6
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Quote:
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No I didnt change the speedo gear.
I can't recall the math but with 31's and stock speedo gear its going to do one of two things, under read Miles or Over Read miles... New gear is now upwards of 80 bucks from what I am told. I would stay with the 3.73's figure a gear change will set you back 1200-1500, that buy a lot of gas.
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Old 02-26-2009, 07:57 PM   #7
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If you fix the speedo gear it will show you the correct mpg and speed. Right now you are about 6 to 10 percent off. This means if you are doing 60 mph on your speedo your actually doing about 66mph. You have to factor in a lot of other things to has it been really windy lately. That will severly affect a jeeps drivability.
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Old 02-26-2009, 08:01 PM   #8
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I have owned the jeep for over a year now. and the mpg has been the same. And from what I see gears are under 400 for front and rear.
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Old 02-26-2009, 08:02 PM   #9
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Thanks for the fast replys. This is just an issue that has been bothering me more and more.

Thanks for the help.
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Old 02-26-2009, 08:06 PM   #10
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I have owned the jeep for over a year now. and the mpg has been the same. And from what I see gears are under 400 for front and rear.
No, problem Case. Gears are about 400 but the labor and extra stuff fluid axle rebuild kit are what get you. Changing gears is a very techinal task. Have you done them before?
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Old 02-26-2009, 08:19 PM   #11
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Like they said above, you definately need to change the speedo gear. I have heard a lot lately about the price of the gear going up, but I just checked yesterday and they are still 20 bucks through quadratec. Is your mileage mixed driving? What I mean by that is are you driving city and highway miles? I have 31's with a 2" BB and get 21 mph on highway. I only get about 12 with just city driving though.
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Old 02-26-2009, 08:48 PM   #12
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My best I ever got with the jeep is 13.xx hwy. City is usually 11 I have even seen 10mpg

I know my speedo is off but damn. that sucks.

My dad is a mechanic. He said changeing the gears is no big deal.
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Old 02-26-2009, 08:50 PM   #13
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If your dad can do it your in good shape, but I believe your going down the wrong path.
Does he want to do mine?
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Old 02-26-2009, 09:31 PM   #14
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I never said I was going to do it. It was just an idea. I dont know what else to try.

I would rather not do it. And my idea was to do it. cuz I thought i had the 3.07 gears.

I checked my gears and they are 3.73. I no longer think its worth it now. But I wanted to see what you guys thought.

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