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Discussion Starter · #1 ·
I have a three speed auto 727 Tranny and I am trying to find out my gear ratio on my rear axle. Do I figure it in 3rd gear or 2nd gear with this formula.

Rpm X Tire Diameter
--------------------- = Gear Ratio
Mph X 336

When I do it in 3RD gear it shows to have like a 3.37 gear ratio but I know gears have been changed out of my new Jeep I just dont know what to.
 

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Official Historian
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In 3rd gear. Sounds like you have 3.31 gears.
 

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It is sometimes hard to "Crunch the numbers" when you have an automatic trans. Because the trans slips a little, and the converter will slip also. And unless you are using some kind of GPS speedo it is hard to actually tell how fast you are going in a jeep that has been changed.

Just mark you tire with some tape, and mark your drive shaft. Pus the jeep so the tire makes one rev. Count how many times the d-shaft goes around. That is your gear ratio.
 
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