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Unread 09-19-2013, 10:45 PM   #1
coltonflak12
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Regear 4.56 with 31s?

So i need new bearings in the rear bad, so i was thinking a gear upgrade since itl be opened up anyway. Right now im stock, but plan on gettin a 2in BB with longer shocks and 31 x 10.50s. I want more power, so would 4.56 be a good choice or no?

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Unread 09-19-2013, 10:57 PM   #2
newfieZJ
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You'll certainly feel more power . I'd like to do this to my 5.9 .

I would think city driving would be improved regarding MPG but hwy would suffer . All in all , I would say go for it and let me know how it goes .
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Unread 09-19-2013, 11:26 PM   #3
riot1987
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this may help
gear_ratio_chart.gif

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Unread 09-19-2013, 11:35 PM   #4
coltonflak12
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That does help alot, so with more power, does that mean alot worse mpg or no? And is it bad to not be close to factory?
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Unread 09-20-2013, 12:03 AM   #5
98GCLimited
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Quote:
Originally Posted by coltonflak12 View Post
That does help alot, so with more power, does that mean alot worse mpg or no? And is it bad to not be close to factory?
From my understanding you might gain a small amount MPG in city driving since the engine doesnt have to work as hard to accelerate but on the highway your RPMs will be higher so it will drink more gas on the highway.

Being around stock on that chart (in the green area) will feel like it did with stock size tires on factory gear ratios. Being over that it will feel like your gears are shorter, higher engine RPMs to achieve the same MPH. It would feel like it accelerates faster and with more power but less top end speed.

4.11s on 31s would be close to factory but if you dont drive much on the highway with it or dont really care about highway MPGs then go for the 4.56s they would probably be pretty nice on the trails and in city driving.

Id like to regear my ZJ one day. Im on 31s and still on the 3.55s (not to mention 4.0L) and its SLOW and gutless
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Unread 09-20-2013, 02:47 AM   #6
coltman151
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Quote:
Originally Posted by 98GCLimited

Id like to regear my ZJ one day. Im on 31s and still on the 3.55s (not to mention 4.0L) and its SLOW and gutless
Yeah, it is a great feeling when you're to the floor in first gear and still losing speed on the hilly mountain roads around here. Lol. And I am considering 33s. Regret-o-meter is already pinging.
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Unread 09-20-2013, 03:33 AM   #7
hondakilla98
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That's why I bought a 5.9. 32's on 3.73's is still faster than a stock 4slow.
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Unread 09-20-2013, 08:27 AM   #8
Technohead
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Keep in mind that this chart oversimplifies a very complicated subject (efficiency).

If you own a Jeep then worrying about fuel mileage is a joke so disregard that side of the chart. Replace the part that says "More Power" with "Better Offroad" and then your choice becomes obvious. 4.56's are never bad for wheeling. It doesn't matter what your tire size is.
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Unread 09-20-2013, 09:07 AM   #9
spidermonkey
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The chart is off, I run 2200-2250 rpm at 65 with 4.56 and 33's. I think you will run about 2500 RPM at 65, right in the power ban. That would be nice with the 4.0.
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Unread 09-20-2013, 09:46 AM   #10
PolkaPower
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If you decide on bigger than 31" tires, you will wish you got 4.56's.
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Unread 09-20-2013, 10:10 AM   #11
JakeC132
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i did the exact same thing this spring except i swapped in an 8.8 also. i'm running 4.56 gears lockers and 31's (for now) the power in the woods is a huge difference. I don't really like to drive it on the highway though. anything over 65-70 is high rpms.
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Unread 09-20-2013, 11:10 AM   #12
HighLonesome
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Quote:
Originally Posted by PolkaPower View Post
If you decide on bigger than 31" tires, you will wish you got 4.56's.
^This. I regeared to 4.10 when I went to 31s. Not much of a noticeable difference from 3.73. In retrospect I should have done 4.56. Or at least I think I should have.
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Unread 09-20-2013, 01:40 PM   #13
coltonflak12
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Would i have to to the front and rear? Or can i just do the rear?
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Unread 09-20-2013, 02:09 PM   #14
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Quote:
Originally Posted by coltonflak12 View Post
Would i have to to the front and rear? Or can i just do the rear?
Your front and rear gear ratios need to match.
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Unread 09-20-2013, 05:11 PM   #15
98GCLimited
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Quote:
Originally Posted by coltonflak12 View Post
Would i have to to the front and rear? Or can i just do the rear?
Quote:
Originally Posted by CatSplat View Post
Your front and rear gear ratios need to match.
^This

You have to do both.
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