Read the question of the month, above your post. The stock gearing on an auto trans Rubicon (4.10) is sluggish. Why would you want to spend the money it takes to re-gear your Jeep to re-gear it to "sluggish". If it is sluggish to begin with, and you add bigger and heavier tires, re-gearing to stock gearing is going to be even more sluggish. You need lower gears to even start to come close to stock performance with the larger tires.
I went with a 2.5" lift and 35" tires on my auto trans Rubicon, and re-geared the differentials to 5.38. I still lost performance relative to stock. It is fine around town, and get up and go from the stop light is fantastic. But out on the highway, when it is in that deep deep overdrive top gear, it has a hard time getting out of its own way, and it still downshifts just to make it over a freeway overpass. I personally think that if they made a gear ratio of 5.88 it would be perfect for an auto trans JK with 35s.
I say go as low as you can. If you have a Dana 30 front end that is 5.13, and if you have a Dana 44 it is 5.38. Definitely don't go 4.88, it will be total waste of your money.
2014 Grand Cherokee Laredo: 2" Eibach lift, 265/70R-17 BFG KO2's, 17x9 KMC Addicts
Last edited by MoparToYou; 07-21-2010 at 09:43 AM.