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post #1 of (permalink) Old 03-26-2001, 06:43 PM
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What gears for 31s on a 4 banger TJ

Im adding 31s to my stock 4 banger TJ (dont laugh a 4 banger is what I wanted) I need to know what gears I'm going to need to keep the engine in its peak power range. I wouldnt mind going slightly lower but not super low and after I change the gears I wont need to replace the speedo gear right? Please help!! Thanks

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post #2 of (permalink) Old 03-26-2001, 07:50 PM
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Re: What gears for 31s on a 4 banger TJ

Well I am not sure of the diff ratio you can do a search her on the board someone posted a site that will calc it for you. I can tell you that you WILL have to change the speedo gear no matter what. ANytime you have a wheel size change you will need to change the it. Or at least that is what I have figured out.

post #3 of (permalink) Old 03-26-2001, 07:50 PM
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Re: What gears for 31s on a 4 banger TJ

Well I am not sure of the diff ratio you can do a search here on the board someone posted a site that will calc it for you. I can tell you that you WILL have to change the speedo gear no matter what. Anytime you have a wheel size change you will need to change the it. Or at least that is what I have figured out.

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post #4 of (permalink) Old 03-26-2001, 07:52 PM
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Re: What gears for 31s on a 4 banger TJ

Thank u

post #5 of (permalink) Old 03-27-2001, 12:20 AM
 
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Re: What gears for 31s on a 4 banger TJ

Some people have put up w/ 33's and a stock 4 banger jeep. Just a thouhgt I'd look for a d44 rear for your tj when you do the gear swap (so you don't put any cash into your d35 then re invest it into a d44) most of them came w/ 3.73 gears from the factory but you would probably be wanting 4.27's ? or 4.56's. Might just be worth while to save the cash and put up with a top speed of 70 and not the quickest acceleration.
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post #6 of (permalink) Old 03-27-2001, 05:49 AM
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Re: What gears for 31s on a 4 banger TJ

I believe most came with 4.10s....

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post #7 of (permalink) Old 03-27-2001, 08:30 AM
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Re: What gears for 31s on a 4 banger TJ

Just don't use 5th gear....that's the cheapest redemy! If you can get off the line without slippin' the clutch too much you're home!
But if that does not sooth your need go here:

http://www.ring-pinion.com/RPMCalculator.html


I would have done the math for you ...but I don't know what size tire you started with. I lost my link to the speedo calibration page. It had a nice chart for which gear was needed to correct for gear/tire changes.
oh...I found it http://auto-toyz.com/Advanced-adapte...b-chart-1.html


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post #8 of (permalink) Old 03-27-2001, 01:22 PM
 
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Re: What gears for 31s on a 4 banger TJ

I wouldn't bother to regear with just 31's. If you have an auto then you have 3.73 gears, and if you have the AX5 then you have 4.10 gears. The next ratio available would be 4.56, and it's hardly worth the effort.
I've had 31's on my four banger for 3-4 years now.

John
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94 GMC Z71 with less "stuff"
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