I have an 08 Unlimited Sahara and a mechanic pretty familiar with Jeeps told me they all (Sahara's) come with the 3.73 gears but I was under he impression they came with 3.21 gears. I know the 3.73 gears are an option because I looked on Jeeps site but is there a way to find out what gears I have in mine without taking it apart?

 

i believe you lift it up, spin the tire and count how many rotations of the tire it takes for the driveshaft to make a full turn.......something like that, its been a long day

 

If you have a 6-speed Sahara without the tow package, you have the 3.21's. If you have the tow package or the automatic trans, you have 3.73's.

 

x2 - That's my understanding as well.....

 

I recently had the same question and I read you can get a "build sheet" from Chrysler about your Jeep.

I went to Jeep.com and filled out the contact form, including your VIN #, and ask them for the build sheet. In a few days I got a response with all the information in an email.

The part I was looking for was in the email...

Next Gen. Dana 30 Solid Front Axle
4.10 Axle Ratio
Next Gen. Dana 44 HD Rear Axle

 

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

Chock the right rear tire, 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 jackstand and lower jack.
Put transmission in gear and/or apply emergency brake.
Remove chocks.

 

You could always read the stamped rear end. It should tell you the gears

 

Unless you paid $50 for the 3.73 option.

Best to request a build sheet. It's good to have anyway.