Ok
I have a stock 08 Unlimited X automatic. I bought 33's mud terrains, 2.5 teraflex BB, steelies. what do I have to modify with gears, and transmission? Do I even have to? Do I need to get the computer flashed?

 

You don't NEED to, but with the automatic I would step up to 5.13's ASAP. It will be the happiest day of your JK owning days.

 

with 33s? I would go 4.88 tops

 

You don't have to do anything. Drive it and see how it feels. I think you'll notice a loss of power, for sure. I don't know about 5:13's but your will want to re-gear. I'm running 33's with an auto but I have 4:10 gears. I just got the Superchips Flashpaq and now I'm pretty happy. I won't re-gear if I stay with the 33's.

 

If your on a budget (like most of us), you can live with you Jeep as is for now. You will notice a slight loss of power, especially at acceleration If you plan to go to 35's in the future, 4:88's or 5:13's will be great...5:13's for 37's.

 

The overall diameter of a so called "33" probably won't be much different than stock tire.

 

Not me man!! I hated my automatic's gear range! Remember I've owned both the auto and stick. Having 5.13's in an automatic is almost equal in final gear ratio to having 4.10's in a 6 speed. That said, if I were back in my auto I would have changed the gearing to 5.13.

 

I think you really have to weigh the drivin environment... if you do any highway driving that fugger is gonna be reving very high at 70mph +

 

Come-on bubba, you know where I live. There ain't nuthin but flat-ass highway down here. Trust me when I tell you that the auto is geared WAY too high. I had stock 32's and hated it even before I installed my 35's, which by the way turned my 4speed auto to a 3speed auto... And that was with 4.10's

 

I need to offer a counterpoint. I have a 09 unlimited auto - just put on 35" Procomp Xterrains (which i was surprised to see are more like 34.3"). I have a 2.5" lift. I don't drive too quickly, but after adjusting the shift points with the AEV procal, I am still very happy with the 3.73s and have no plans to change them - granted i live in houston and its pretty flat here).