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Old 03-25-2013, 09:01 PM   #1
Join Date: Mar 2013
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No power after lift

Just finished lifting my 98 sahara 4.0 5spd. 3.73 gear, with rough country 2.5 lift. I put 32/11.50-15 Falken Rocky Mth tires on 8 inch Ion wheels. The jeep had 30/9.5-15 with gambler wheels on it stock and had great power, after the lift and tires it seems to have hlf the power, it only has 95k miles. Do I need to change to a 31 inch tire?

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Old 03-25-2013, 09:28 PM   #2
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You just severly changed your gear ratio with the 2" larger in diameter tires. 3 choices... go back to the original tire size, regear your differentials, or live with what you have. 31's would get some of it back, but not all.

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Old 03-25-2013, 10:10 PM   #3
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I had a 4 cyl. and it had the same tire and lift with more power
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Old 03-26-2013, 01:33 AM   #4
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the 4 cyl came with 4.10 gears, not sure if that makes much difference
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Old 03-26-2013, 11:55 AM   #5
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Yea I know that but with the regear calculator it only shows needing 3.90 gearing, this thing bearly wants to pull 5th gear, and the torque the 4.0l has should compensate for the 2.5L gearing right?
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Old 03-26-2013, 12:05 PM   #6

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Some power loss is normal, bigger tire etc.. jeep is sitting higher etc.etc.. that being said.
I had a 01 with 3.73 on 33's and 5spd.. as i recall it was okay.. only time I had an issue with 5th was if I was going up a big hill etc.. then might need to go to 4th or in rare cases 3rd. Perhaps it just needs a tune up.
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Old 03-26-2013, 12:09 PM   #7
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I agree. I don't have a ton of experience with Jeeps, but I've modded my trucks with lifts, tires etc. Half the power that it used to have seems extreme. With only 32" tires, 3.73s should be plenty. I'd look for a possible (and coincidental) mechanical issue.
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Old 03-26-2013, 12:17 PM   #8
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I'm running 2" springs, 1 1/4" body lift, 4.0l, 3.73's, and 32" Falkens, 5 speed. It's no race car, but it gets out of it's own way, and pulls 5th gear pretty well. And this is @7500+ ft. elevation.
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Old 03-26-2013, 09:10 PM   #9
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I went from 31" tires to 33" and kept the 3.73 gearing. I also have the 6 speed transmission, so 5th is still useful unless I'm pulling up a big hill doing less than 50 or so. 6th is only good for maintaining highway speed. You losing half the power seems extreme, you may have other issues. I just had to change my shifting habits and it's almost as good as it was before.
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Old 03-29-2013, 09:42 PM   #10
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Had time to work on the Jeep today and found the problem, Toe end was out 2 inches and had a bad hub assembly, I had already wore the tires after 200 miles, runs and drives super now.
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Old 03-29-2013, 09:56 PM   #11
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The loss has to do with the weight of the tire more than the size when going from 30 to 32. My 31's cut the power on my 3.73's because I went from a street tire to a km2. I would look at a regear after you bump to 33's...which will happen sooner than you think.

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