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Unread 07-22-2010, 01:58 PM   #1
MilitaryJK4455
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Want to know your gear ratio for sure?

Thanks ronjenx, for writing this out for us.

Finding Your Gear Ratio

Here is a procedure to get the axle ratio when it is not known. Build sheets (available from your dealer, or from the Jeep web site) will only tell you what the Jeep had from the factory. A used Jeep could have been re-geared.

If you want to know for sure, and remove all doubt, do this:

Chock the front tires, fore and aft.
Put the transmission in neutral.
Emergency brake off.
Jack the left rear tire off the ground.
Put a jack stand under the frame, just in case the jack fails (had to add this).
Put an index mark on the aft end of the drive shaft, visible from the left rear wheel.
Put an index mark on the left rear tire at the 6 o'clock position.
Rotate the left rear tire 2 complete revolutions while counting how many times the index mark on the drive shaft passes its original position.
That number will be your axle ratio.
Remove jack stand and lower jack.
Put transmission in gear or Park, apply emergency brake.
Remove chocks.
If you have limited slip, jack up both rear wheels and rotate one revolution, making sure both tires rotate equally.

If the drive shaft rotated almost 3 1/4 turns, you have 3.21
If the drive shaft rotated almost 3 3/4 turns, you have 3.73
If the drive shaft rotated a little over 4 turns, you have 4.10
If the drive shaft rotated a little under 5 turns, you have 4.88
If the drive shaft rotated a little over 5 turns, you have 5.13

Now go drink a beer and feel confident that you know your gear ratio without a doubt

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Unread 07-22-2010, 03:35 PM   #2
fernjack
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That IS a very good write-up .........but I think I'll just drink a beer
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Unread 07-22-2010, 03:52 PM   #3
MilitaryJK4455
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Originally Posted by fernjack View Post
That IS a very good write-up .........but I think I'll just drink a beer
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Unread 07-26-2010, 07:47 PM   #4
wrestlerobx
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CRAWLED this is cool. I appreciate it
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Unread 07-26-2010, 08:03 PM   #5
MilitaryJK4455
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Originally Posted by wrestlerobx View Post
CRAWLED this is cool. I appreciate it
There is a lot more stuff where that came from... Just check out this sticky...
http://www.jeepforum.com/forum/f96/j...reads-1074059/
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Unread 07-26-2010, 08:08 PM   #6
wrestlerobx
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yeah ive been peeking in there but i must have missed this one i suppose
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Unread 07-27-2010, 11:27 AM   #7
CarolinaPoetic
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fore = front
aft = rear
and beer = blue moon!
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Unread 01-12-2011, 12:42 PM   #8
OLDGUY19
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Thank you
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Unread 01-12-2011, 02:37 PM   #9
jstrubberg
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Or just get your Jeep up to 70mph, recrd the RPMs then check them against the chart floating around here. Lot less work.
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Unread 01-12-2011, 02:40 PM   #10
MightyLampshade
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You can also count the teeth on the gears if you have the diff covers off and a little simple math will provide the ratio as well
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Unread 01-12-2011, 03:05 PM   #11
propped1
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Originally Posted by MDragga79 View Post
You can also count the teeth on the gears if you have the diff covers off and a little simple math will provide the ratio as well
Dont think this is an easy way.

Take the cover off, dispose of gear fluid, fill with more gear fluid.

50 bucks and an hour to check your teeth? think you're missing the point....
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Unread 01-13-2011, 09:26 AM   #12
MightyLampshade
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Quote:
Originally Posted by propped1 View Post
Dont think this is an easy way.

Take the cover off, dispose of gear fluid, fill with more gear fluid.

50 bucks and an hour to check your teeth? think you're missing the point....
You'll note I said "if you have the cover off" There was also no mention in any previous post about cost, merely a way to find out your gear ratio

I think you missed the point...
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Unread 11-29-2012, 05:07 PM   #13
riot1987
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I have a ring gear with 41 teeth and a pinion with 14. Can one of you kind gentlemen give me my ratio? Do you just dived the two numbers? 2.92's..?
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Unread 11-29-2012, 05:49 PM   #14
Taguilar
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Quote:
Originally Posted by jstrubberg View Post
Or just get your Jeep up to 70mph, recrd the RPMs then check them against the chart floating around here. Lot less work.
You know where I can find this magical chart?
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Unread 11-29-2012, 07:49 PM   #15
ronjenx
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Quote:
Originally Posted by riot1987 View Post
I have a ring gear with 41 teeth and a pinion with 14. Can one of you kind gentlemen give me my ratio? Do you just dived the two numbers? 2.92's..?
You did the math correctly.
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