Baystate Jeepers

I'm not sure what gearing I have, when I had the skids put on they mentioned it wasn't printed on the differential cover. I had Chrysler email my build sheet and I think I have 3.73, but not sure if I'm reading the right number.

Next Gen. Dana 30 Solid Front Axle DMEP 3.73 Rear Axle Ratio DRZS Next Gen.
Dana 44 HD Rear Axle DSAP Anti-Spin Differential Rear Axle DS7S Conventional

If that is a 3.73 instead of 3.21, would I need gearing to support 35's ?

There is only one way to be sure if you dont have the tag. Open the cover , drain the oil , and count the teeth on both the Ring and Pinion gear. Its usually printed on the ring gear edge so as you rotate it you could read it. I assume its a V-6 JK ? Which year makes a difference also. To give you a fair answer on gearing , Id say look at a Tire Vs. Gear ratio chart. It will show you the RPMs you turn at 60 MPH (1 mile per minute) Now look what RPMs your turning with 35s. You would want to be the same or a little more than stock , if you like the way it drives now. The biggest problem with suggesting what ratio to pick not knowing what you do with the Jeep , (DD) how many miles you drive or is it a dedicated woods machine ? Therefore pick the ratio the gets it a little above the stock ratio. Thats all based on 35s and would be different if down the road you want 37 ! Doin it once is our goal. Hope this explained what to look for. I personally run 4.56s with 35s . Every day I kick myself for not doing 4.88s . I went 300 over stock 3.73s with 32s and if I had gone with the 88s it would have been 800 RPMs and I thought that would be to much. I have a 4x1 T-Case so in low range Im good , unless you have a Rubicon you dont . FjR68

the factory build sheet is very reliable for a 16 Jeep and yes you have 3.73 gears


I have a 2012 with the newer penstar engine and have been running down the road on 35's for about a year now. Mileage is not great but it starts stops and moves down the road fine. I do have a stick which makes it manageable and I use 6th gear on the highway frequently.

This site (link) may help you figure out where you are currently, and where you may end up. Take your engine size and transmission type, see where you are, and if you were to upgrade to 35's, what the differences would be.

Thank you to all. I may have found a plan after talking to Scott.

Plans are great! but are always changing. I had to keep a list with what the origional plan was and then the changes and WHY the change was made, then again it was a large build but it helped when I ended up somewhere and wondered why I didnt do something else.