Hey guys, I just bought a 2010 Jeep JKU but have no idea what gearing it has! Anyone know of any way I can tell if my Jeep has the 3.21 or the 3.73 gears? (aside from opening up the diffs of coarse)

 

Search your VIN with the dealership and have them look up what options were on the Jeep. I think theres a way to do it online too.

 

Any idea where online I could find that? Jeep website or something?

 

Go there and then select "equipment listing". After that you can type in your VIN and you'll get the build sheet as pdf.

 

Lift a corner/end, mark the driveshaft/tire/ground, spin a tire, count driveshaft revolutions.

The build sheet you can get from the dealer/jeep website will list what it left the factory with. Did the previous owner regear?

 

https://jeep.custhelp.com/app/jeep/e...WGxOMmc2T2w%3D

 

Having bought it used, there is no guaranty the build sheet will reflect what gears are in it now.

Here is an easy method to check the gear ratio:

Jack one front tire off the ground.

Put a chalk mark on the tire and the drive shaft.
Rotate the tire by hand 2 complete revolutions while counting the drive shaft turns. The number will be your gear ratio.
A little less than 3 and 1/4 turns will be 3.21 gears.
About 3 and 3/4 turns will be 3.73 gears.
A little over 4 turns will be 4.10 gears.

 

Thanks for all the help guys! It's a stock jeep. I'm pretty sure the only thing they ever did to the thing was slap some 18" mall crawler rims and beefy street tires on it.lol But thanks to ya'll I totally figured it out. I did the lift one corner trick and then cross checked the calculations with the equipment list on the jeep website...DEFF 3.73's. Looks like the 35's won't be too much of an issue until i can save to re-gear.

 

You will be a tortoise on the road bro! I have a 2011 and put 33's on and couldn't use 6th gear at all. I regeared to 4.88's and 35's and doin great...JMO I guess it depends if you have an auto or stick, but I was dragging the road behind my rig. Sent from the swamp while taggin' a gator!

 

Yea? I've heard it's somewhat manageable with 35's on 3.73 but on 3.21 it's horrible. Huh...well maybe I'll just run 33's until i re-gear. I just got my 3.5" Rubicon Express Lift in so I'm trying to figure out tires. I know I want the Duratracs.