I have an 09' X 2 doors with the 6 speed manual tranny. It has a 3.21 ratio. I have noted the same car with an automatic tranny gets the 3.73 ratio.
Is that to compensate for the auto tranny ?
Would the 3.21 on a manual the best way to get great mileage ?

3.21 gears will be more economical on gas. With a standard, and six speeds, if not planning on going with larger tires, will perform adequately. The only issue is torque in first gear. Not enough of a major issue to justify using lower gearing from the factory on the standards I guess. This will be a major incentive to re-gear once it is decided to go with larger tires. If really into wheeling and deciding to re-gear, selecting gears that will really give good torque in first and allow the jeep to crawl without much regards for economy is sometimes the case. I suppose re-gearing can result in a "kid in a candy store" type mentality and result in much lower gearing than really needed? Decisions, decisions, decisions ....its what makes the ownership experience so special.

The 3.73 gears are an option, 3.21 is standard (except Rubicon). My manual X has 3.73.

^ Good point.

the auto has a higher overdrive ratio than the manual. the lower rear end gears are to compensate.

no like daggo said its an option you can get in any x/sport or sahara i have a 6 speed X with 3.73. its becasue jeep knows a lot of people want fuel economy 3.21 and others want to offroad with more torque 3.73 options options gotta love a jeep

I was actually just talking to my coworker about this. He has an 07 wrangler with 4.10 (automatic) and I just called the dealership during lunch to find out what my 09 with automatic had, turns out I have 3.73. (Good thing too, looking at getting some 33X12.50R17 Cooper Discoverer STT tires in the coming months!) With 33's I def want to have that higher ratio like 3.73....would be a PITA with 3.21

3.21 isnt an option for the automatic transimission. it is however for the manual. and like its been stated with the 3.21 gears, if you want any tire size bigger than stock you will need to regear.

For 2007 at least, the spec sheet says that included with the Trailer Tow Group option was the 4.10:1 rear end ratio. The 4.10:1 ratio was included with the automatic transmission option in 2007 as well, again according to the spec sheet.

My 07 Sahara (stock) with the six-speed manual and the Trailer Tow option really has a stump puller 1st gear. It also turns about 2200 rpm @ 60mph in sixth gear as I best remember. Still gets 19 to 20 mpg for most driving, I'm happy with the whole package.

DeanLinAZ
2007 Sahara 2-door

For those with auto tranny and 3.73 gears... when you go to 33's you can almost forget about using OD... at least that's my experience so far... ANY small incline tranny drops to 3rd, so I leave it there

That's what the OD off switch in front of the shifter is for

When I go to 35's I'm going with at least 4.88... maybe 5.13. Reasoning is the 3.8 is a torqueless wonder

FWIW, my 09 came with 3.73 gearing with the auto from the factory.
Dealer saaid it was because of having the tow package.
I might consider going to 5.13 but not really sure.