I was looking at the gear ratio table in the 4wd magazine and noticed something odd. I have a jk with 3.21 gears as the factory sticker said and now i am running 33's. On the chart it says 3.21 ratio at 65 mph in 4th gear will give me an rpm of 2124. I am hitting something like 31-3200 rpm which is more like 4.56 gear ratio. Whats going on here? Did the factory make a mistake on my sticker or what?

 

A couple of things come to mind. First, the charts that you are looking at probably assume that 4th gear is a 1:1 ratio. In our JKs, 5th gear is 1:1. Second, if you are looking at the standard equipment list on the left side of the sticker, all JKs, except the Rubicon, come standard with 3.21s. 4.10s are an option and will be shown on the right side of the sticker. Check there to be sure that you don't have 4.10s. If you have the trailer group, you have them and they were available as a sepatrate option as well.

HTH

 

Ihave an '08 2 Door X with the 6 speed and tow package and "heavy duty suspension" option with 255/75R17 (32") Goodyears. Mine came with 3.73 gears as per the right side of the window sticker. I haven't paid attention to the RPMs at speed but will do so tonight and get back to you.

 

You are right - The 08s have 3.73s with the tow pkg unless it is a Rubicon, which comes with 4.10s. The 07s have 4.10s with the tow pkg.

 

Okay .. so now I am confused.

my JK came stock with 3.73's noooo tow package. When I went in to get new Susp. System we had to double check the gears to make sure it would work and figure out what else needed to be replaced.

Come to find out . I do have 3.73s, I DID have to buy new driveshafts that are extended, slip yoke case .... my gears I can go to 4.88s or 5.13s .. he took about a week to figure out what i could upgrade too ..

when I was all stock and no mods done ... my rpms/speed

around 2000 - 2100 rpm in 6th

1500 1st - 5th


NOW :

6th: 2400 - 2500
5th: 2000
1 - 4th : 1400/1500 - 2000 ... depending on how fast I am going ...

I have to go up to about 2500 until I change gears .... its also a gas hog. I used to get 20 in town and 22 on highways ..

10 - 12 in town and 14 about MPG now .... ahhhhhhhh

also running 35's on 17x8" wheels

so save up and do gearing with the lifts and wheels would be my advice.