Im new to the jeep world so this may be a simple question for most but ill include all the info so there is no confusion......So I found out my 2012 Sahara automatic 4 door has 3.21 differential gears. I'm collecting parts now to lift it this coming spring. My question is, I plan on running a 295/70-17 which has a tire height of 34.4" which replaces the stock 32" tires, now obviously I will loose some bottom end. If I went with 3.73 gears will this replace the loss from the addition tire height. Also I can score a used set from an 09. Will these work. Are all JK differentials interchangeable, meaning will a set of gears from a Dana 35 front from an 09 fit a 2012? Same goes for the rear Dana 44? Anyone recommend just going with 4.10's even though 95% of the time it's on the highway and gas mileage is somewhat of a concern ( I'd like to keep the 18-20mpg it's getting)

 

The cost to re-gear from 3.21 to 3.73 is just not worth the marginal performance gain in my opinion....unless you are able to do the work yourself and the parts are free.

All of the X, Sport and Sahara gear sets will interchange. The gear sets from a Rubicon will not interchange with X, Sport or Sahara.

Oh, and it would be a D30 in the front not D35.

 

I have a 2007 x jku with 6spd 35" tires and Im running 4.56's and I love it . I dont get the kind of mileage your getting but its a jeep I dont expect to. On the highway Im getting about 15-16mpg and in town 13.5-14.5, I drive pretty hard so you should probably be able to get better than I am.