So when I'm driving at 60mph my rpm's are at 2000. I'm an auto 2010 on 37s. I got the mph from my gps because the speedo is off anywhere from 4 to 8 mph. Superchip flashpaq on the way! But I don't know what gears are In it...I don't think they are stock because they pull the tires great...also, I am getting like 12.5 mpg in town...how do I increase that?

I'm new here and excited about my jk!

 

Programming the correct tire size will straighten out the poor mileage calculations.

Here is how to find your gear ratio:

Place chocks in front of and in back of the right rear tire.
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 rearmost 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 and/or 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 3¼ turns, you have 3.21
If the drive shaft rotated almost 3¾ turns, you have 3.73
If the drive shaft rotated a little over 4 turns, you have 4.10

If the drive shaft rotated 4½ turns, you have 4.56
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

 

Or he can just register his jeep on owners.jeep.com with his VIN# and it will list what gears he has......just sayin'

 

Not reliable. (And not as quick...just sayin')
He said he suspects the gears have been changed.
A build sheet wouldn't shed any light on his question.

 

Missed the part on him switching gears, my apologies....just sayin'

 

Thanks guys, that description of what to do is confusing to me. Is there any other way to tell what gears?

 

That is the most detailed answer I have ever seen for that question.

 

The OP says it's confusing, so it's useless instruction.
(Which is strange, because it's written for someone who has never done this before.)
Maybe he should take the diff cover off and count teeth.

 

I don't know, that detailed of an explanation was a gift. It seems terribly inappropriate to count teeth.

 

What does "fore and aft" mean on the chock? And the "aft" end of the driveshaft I am guessing is the "aft" in driveshaft?