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Unread 06-08-2010, 11:17 PM   #1
sethkins88
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3:73 gears and 35s with a 3 speed Auto

Im trying to figure out if my gears have been redone. Im running about 3200 rpms at 70mph. My speedo is off my 5mph as well. Just wondering if you guys are running similar rpms with the same setup.

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Unread 06-09-2010, 12:06 AM   #2
Imped
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Going by the math, you should be at ~2500 RPM with 3.73 gears and 35's. It sounds like you have 4.88 gears if you are indeed traveling in the 65-70 mph range.
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Unread 06-09-2010, 12:35 AM   #3
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Indeed. It sounds like the PO regeared it for you. I wonder if you were lucky enough to get a c-clip eliminator kit with the Jeep too.
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Unread 06-09-2010, 08:45 AM   #4
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Quote:
Originally Posted by sethkins88 View Post
Im trying to figure out if my gears have been redone. Im running about 3200 rpms at 70mph. My speedo is off my 5mph as well. Just wondering if you guys are running similar rpms with the same setup.
Speedo is off 5 MPH which way?

If you are 3,200 RPM at 65 MPH, your gear ratio is probably 4.56.

If you are 3,200 RPM at 75 MPH, your gear ratio is likely 4.10.

Your actual tire height and the innacuracy of your speedo are the (2) unknown factors that are making it impossible to say with certainty.
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Unread 06-09-2010, 10:41 AM   #5
INEEDZUSERNAME
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I was @ ~3Krpm with 4.56gr @ 70mph
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Unread 06-09-2010, 11:03 AM   #6
ssdude
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I run 3000 rpm @ 70 mph- 35" tires- 32rH auto- 4.10 gears- I changed my speedo gear a 34 tooth if I remember right. Checked my speed with GPS and with another vehicle.
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Unread 06-09-2010, 11:28 AM   #7
cvd
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You could jack up the rear, manually twist the drive shaft one turn (put t-case in neutral), and count the wheel rotations.
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