Determining gear ratio question -
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Unread 09-10-2001, 08:15 PM   #1
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Determining gear ratio question

How can I determine the gear ratio of an axle already out of the vehicle --no tags --dont want to start pulling the cover --etc fromthe revolutions of the yoke to the wheel
1 to 3/4 or wheel to yoke 1 to 1-1/2 can I calcualate the ratio if known to be within 3.07 to 4.88 range ????

2001 Cherokee limited 94 Cherokee country 93 Wrangler
My former jeep's - 84 CJ7 great trail rig ,79 Cherokee Chief S,75 CJ5 golden eagle W/a 350 in it
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Unread 09-27-2001, 01:03 PM   #2
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if you know what truck it is out of you can try and click on gear calculator

"If you don't plan, you plan for failure"
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Unread 10-02-2001, 07:40 PM   #3
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you can get a rough idea... jack up the car, spin the wheel one complete revolution and count how many rev's the driveshaft makes. for example, if you driveshaft spins 3 times for 1 turn of the wheel, you most likely have a 3.07 or something in that ballpark.

To be more exact, what you need to do is open the diff cover, count the teeth on the ring gear and count the teeth on the pinion, and divide the two numbers. there's your ratio.

Robert Gorrell
1995.5 Isuzu Rodeo - SAS'd and SOA'd, sitting on 36x12.50 TSLs, D44 front, 14bff rear, locked by OX and Detriot, suspensions by Jeep and Chevy, high steer conversion, 5.13 gearing and Teralow in the case. - website
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Unread 10-03-2001, 04:19 PM   #4
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The axle ID number as well as the gear ratio should be stamped on the back side or the right tube. Look for a set of factory stamped numbers, the feds require them to be there before it leaves the factory, you may have to clean-off a few layers of grime to find'em but they're there!
Black 91' YJ with fresh 4.0, Sitting on 31x11.5 Mickey Baja MTX's on 15x10 AR767, Borla Stainless cat-back, free flow cat, it seems like I keep breaking necessary parts just about the time I get enough money together for the fun stuff!!!
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Unread 10-03-2001, 06:35 PM   #5
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I tried the lift up tire and spin thing and it came out 1:1. I know this isnt possible so is there a trick? I put the car in N and my friend and i slowly spun the rear wheels in the same direction....everything was marked and i got 1:1. Its got 30" tires if that makes any difference.
97 TJ w/ Hardtop/AC/5-speed/I-6/ aftermarket stereo/ 2" spacer/1"BL/ 32x11.50 BFG AT's.
....that sounds expensive..
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