How do I determine my gear ratio?

hunter1

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Joined
Jan 17, 2019
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Location
Lafayette, LA
I’ve checked the FAQ info here and not sure about the rear.... looks like Dana 35 but look at that tag... what’s the ratio?

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3.07

Hang in there, at least you have a Jeep! And 3.07 is a good justification for regearing.
 
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Haha ok thanks! It’s a 2002 automatic if I didn’t mention that. My buddy had it for almost 5 yrs prob didn’t put 1000 easy miles.

Its on tires 285 70R17 ...equivalent is 32inches...guess that isn’t helping.

Last night when driving it home was turning 1900 rpm at 60mph.

No big deal at present my hardcore wheelin mudding days are about over, I’m mostly a paw paw driver now, easy drive to hunting camp etc.


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3.07 is the absolute worst, which is what is in mine, a 2002 5 speed 4.0l. When I purchased it, I thought I was getting 3.73. I added a set of 31x10.50-15 tires(actual height 30.5") that night when I got it home, and that didn't make it any better. I don't use 5th gear on the interstate, and reverse in high range is just too fast. Probably doing 4.56's this summer....
 
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If i were you i would pick up front and rear 3.73 axles. They are readily available therefore easier on the pocketbook and a direct bolt in.
Would save the cost of a regear.

I like my 3.73s both on my auto and my manual 6 speed.

Would work if your Jeep is a DD and not a hard core trail rig.

@JMT may have a 3.73 Dana 35 for sale.
 
If i were you i would pick up front and rear 3.73 axles. They are readily available therefore easier on the pocketbook and a direct bolt in.
Would save the cost of a regear.

I like my 3.73s both on my auto and my manual 6 speed.

Would work if your Jeep is a DD and not a hard core trail rig.

@JMT may have a 3.73 Dana 35 for sale.
Yeah, the 3.73 Dana 35 will be going up for sale cheap, maybe $200 complete.
 
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1) On the rear differential, on the left side of the housing/cover, there is often a strip of metal with numbers or letters on it. Decipher
2) type your VIN into this website to retrieve your factory build sheet
https://fcacommunity.force.com/RAM/s/equipment-listing
3) wrap a piece of string around your drive shaft and mark the string. Rotate the axle one time and count the number of times it turns the driveshaft (~ 3 is 3.07; almost 4 is 3.73)
 
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1) On the rear differential, on the left side of the housing/cover, there is often a strip of metal with numbers or letters on it. Decipher
2) type your VIN into this website to retrieve your factory build sheet
https://fcacommunity.force.com/RAM/s/equipment-listing
3) wrap a piece of string around your drive shaft and mark the string. Rotate the axle one time and count the number of times it turns the driveshaft (~ 3 is 3.07; almost 4 is 3.73)

Thanks man
 
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2001 TJ, I verified the build sheet says my rear is 3.73 and the speedometer gear is 31 teeth for 33" tires. I rotated the gear housing to the proper marking for 31 teeth. Now the speed is reading 10mph high. (when I drive 55mph speedometer says 65mph).
When the setting was rotated to higher numbers because I thought it was determined by the tire size and not teeth, the reading was more accurate.
What else could be causing the speedometer to read incorrectly if the settings match the owners manual and all the links posted to verify this?
 
Could you clue me in as to how you can tell? I'm curious about mine as well.
Look at the axle tag bolted to the 9 o'clock position of your differential cover, that tag has your ratio stamped into it.

This tag is indicating the axle gears inside have a 3.73 ratio. If your axle still has this tag odds are high that it was not regeared and that it still has the same ratio gears the factory installed.

78118
 
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Jerry,
Here is what I found from 2015 -
3. Jack up the rear end. Count driveshaft revolutions while rotating the tire. Turn the tire 2 complete rotations if your other tire remains stationary and does not rotate. Turn the tire 1 complete rotation if the other tire turns in the same direction. The number of times the driveshaft rotates equals the gear ratio. If the driveshaft rotates about 3x, the gear ratio is 3.07. If it rotates 3 3/4 turns, the gear ratio is 3.73. You can mark the driveshaft to help you count. NOTE: see post below if interested why you spin a tire 1 rotation or 2 rotations.