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Old 11-20-2010, 02:50 PM   #1
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Change Gears better Highway Miles

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I have a 04 TJ X auto with 6 inches of lift running on 33" tires.
So I'm considering changing my gears for better highway miles. What would be the best ratio for this kind of travel?
Remember it's a auto

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Old 11-20-2010, 05:45 PM   #2
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For 33" tires and your 4-speed automatic transmission, 4.88 is the best all-around ratio.

YES I KNOW 4.88 sounds like it would way too low of a ratio for 33" tires but your particular transmission has such a steep overdrive ratio that it needs an extra low ratio like 4.88 to compensate for it. You would be sadly disappointed if you only went with 4.56 as some who aren't knowledgeable about your particular transmission may try to convince you to go with.

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Old 11-20-2010, 06:26 PM   #3
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This forum is awesome. The things I learn in just one response. So, that being said, does this apply to all years, such as a 2007 with 33s and an Auto?

What is "regearing"? Is that swapping out the gears inside the tranny itself? If it is an Auto, why can't a programmer reprogram the ECU like when you can adjust for tire sizes?
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Old 11-20-2010, 06:31 PM   #4
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Regearing means to change the ring & pinion gears inside the axle to lower ratios (4.88 is, in gear-speak, a lower ratio than 3.73 is). In the case of a 4x4 vehicle, that means changing the gears inside both axles. Yes that would be applicable to your 2007 as well. Lower gear ratios inside your axles will produce higher engine rpms... what you need to do to compensate for larger diameter tires since engine rpms get reduced with larger diameter tires at the same highway speed. The problem with that is those lower rpms produce less power than you had before with the previous smaller tires. Regearing so you get higher engine rpms restores the power lost after installing bigger tires.
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Old 11-20-2010, 06:33 PM   #5
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regearing is the ring and pinion gears in the front and rear differentials-not tranny,, yes all yrs can regear
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Old 11-20-2010, 07:17 PM   #6
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Thanks all.....but cant you just drop down into 2 on the auto shift lever up to a certain mph, then slap it up into Drive? Or is this bad Jeep etiquitte for longevity?

As for restoring lost power without regearing, what size tires are suggested to go down to from 33s on 18" wheels to get some of that power back?
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Old 11-20-2010, 07:20 PM   #7
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The original poster asked about mileage. The mileage may improve a bit but given that changing the gears is going to cost over 1k, you are not going to recoup that in gas.
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Old 11-20-2010, 09:16 PM   #8
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Thanks for the info. I actually can get it done really cheap here in town. I'm looking for the best gas mileage and 4.88 does sound a bit low. Has anyone done this? I travel to an from work highway almost everyday.
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Old 11-20-2010, 09:44 PM   #9
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4.88 for the 4 speed auto is the best for getting that "pep" back that you had with stock tires.Do not plan on going over 70mph for long periods of time though.
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Old 11-21-2010, 05:15 PM   #10
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Any opinion on 33s on a 4 banger? Which gears should I look into? I'm usually cruising at 60-65mph on the highway. Tiny bit of offroading
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Old 11-21-2010, 05:21 PM   #11
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Quote:
Originally Posted by zksimsnv View Post
Thanks for the info. I actually can get it done really cheap here in town. I'm looking for the best gas mileage and 4.88 does sound a bit low. Has anyone done this? I travel to an from work highway almost everyday.
4.88 only sounds too low to those who are inexperienced at this. For YOUR particular transmission and 33" tires, 4.88 is the appropriate ratio. You would regret 4.56 rather quickly. Just like the previous owner of my TJ regrets having installed 4.88 gearing for 35" tires, 5.13 to 5.38 is the appropriate ratio for 35" tires and that same transmission. I own it now and the 4.88 gearing with my 35" tires makes it a real dog on the freeway, I am always having to shut the overdrive off for even mild grades.
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Old 11-21-2010, 05:23 PM   #12
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I have the 4 banger and just lifted it and put 33's on it. I then re geared it with 4.88 front and rear and that was the best thing I did. it got me alot of my lost power back (and with a 4 banger every little bit helps). My gearing is now back to what the stock tire/gear ratio was and the speedo is just about dead on. if your going to put 33's on then plan the cost of gears into your tire and wheel package. YOU WILL NOT REGET IT!!!

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