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Jeep Wrangler JK
JK General Discussion
Axles
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<blockquote data-quote="Anybodyhome" data-source="post: 438623" data-attributes="member: 19161"><p>This chart is based on <strong>65 MPH</strong> and a gear ratio of 1:1, on a manual transmission in 4th gear. Please NOTE: If you have an automatic transmission your RPM will higher due to slippage in the transmission and the torque converter. With an overdrive transmission your RPM in overdrive will be 15% to 30% less than indicated.</p><p></p><p></p><p>[ATTACH=full]119053[/ATTACH]</p><p></p><p>This is pretty accurate. My 2014 3.6 5-speed auto w/3.73 runs about 2200 or so at 70mph on 35" tires.</p><p></p><p>While you may think you know your Jeep's gear ratios based off its year and/or differential type, if the vehicle was purchased used then someone may have changed them at some point in the past. So an easy way to determine your actual gear ratio is to check the tag attached to the differential cover by the cover bolts. On the tag there should be some numbering such as 3.54 or 3.73, either of those numbers will give you the stock axle ratio. To verify, or to see if that ratio has changed, you can jack up the rear axle and support it with jack stands. With the transmission in neutral, rotate the rear driveshaft by hand. Count the number of driveshaft revolutions required for one revolution of the tire. </p><p> </p><p>If the driveshaft turns approximately 3-1/2 times, you have a 3.54 ratio, etc. It is helpful to use a grease pencil or chalk to make a reference point on both the tire and driveshaft while performing this test.</p><p></p><table style='width: 100%'><tr><td>Number of Turns</td><td>Approx. Gear Ratio</td></tr><tr><td>3</td><td>3.05 : 1</td></tr><tr><td>3 - 1/2</td><td>3.54 : 1</td></tr><tr><td>3 - 3/4</td><td>3.73 : 1</td></tr><tr><td>4</td><td>4.10 : 1</td></tr><tr><td>4 - 1/2</td><td>4.55 : 1</td></tr></table></blockquote><p></p>
[QUOTE="Anybodyhome, post: 438623, member: 19161"] This chart is based on [B]65 MPH[/B] and a gear ratio of 1:1, on a manual transmission in 4th gear. Please NOTE: If you have an automatic transmission your RPM will higher due to slippage in the transmission and the torque converter. With an overdrive transmission your RPM in overdrive will be 15% to 30% less than indicated. [ATTACH type="full" alt="1623415934484.png"]119053[/ATTACH] This is pretty accurate. My 2014 3.6 5-speed auto w/3.73 runs about 2200 or so at 70mph on 35" tires. While you may think you know your Jeep's gear ratios based off its year and/or differential type, if the vehicle was purchased used then someone may have changed them at some point in the past. So an easy way to determine your actual gear ratio is to check the tag attached to the differential cover by the cover bolts. On the tag there should be some numbering such as 3.54 or 3.73, either of those numbers will give you the stock axle ratio. To verify, or to see if that ratio has changed, you can jack up the rear axle and support it with jack stands. With the transmission in neutral, rotate the rear driveshaft by hand. Count the number of driveshaft revolutions required for one revolution of the tire. If the driveshaft turns approximately 3-1/2 times, you have a 3.54 ratio, etc. It is helpful to use a grease pencil or chalk to make a reference point on both the tire and driveshaft while performing this test. [TABLE] [TR] [TD]Number of Turns[/TD] [TD]Approx. Gear Ratio[/TD] [/TR] [TR] [TD]3[/TD] [TD]3.05 : 1[/TD] [/TR] [TR] [TD]3 - 1/2[/TD] [TD]3.54 : 1[/TD] [/TR] [TR] [TD]3 - 3/4[/TD] [TD]3.73 : 1[/TD] [/TR] [TR] [TD]4[/TD] [TD]4.10 : 1[/TD] [/TR] [TR] [TD]4 - 1/2[/TD] [TD]4.55 : 1[/TD] [/TR] [/TABLE] [/QUOTE]
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Jeep Wrangler JK
JK General Discussion
Axles
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