They're geared that way since the majority of the torque is I. The upper rpm ranges on the 3.6, even more so than the 3.8's. I'm running 35's with 4.88's on my 6-Speed 3.8 and it made a huge difference from the 3.21's! As has been mentioned You need to do the Math or find a chart (where someone else has done the math) before
choosing your ratio though. Get it wrong and it'll be costly to redo.

RT

 

I have a pretty new 2012 unlimited rubi auto. It has the 4.1 gears. With 34.4 inch Falken Wildpeaks I have zero performance problems. It drives great at both highway (70-75) and in town. Acceleration from stop in town is fine. If you plan to stop at 35 in tires I would say the 4.1 gears will be fine. Also keep in mind that the computer is in breaking mode for the first 300 miles. Make your judgement after that. I would definitely not want to "daily driver" anything less that 4.1 with 35s in a 2012 unlimited.

 

If its geared correctly you shouldn't have to turn off the overdrive...I would rather turn a higher rpm and have the added torque anyways. Not to mention a lower crawl ratio off road

 

Ive driven a 35" tired 2012 Unlimited with 3.73 some, and it runs just fine.

3.21 would suck Im betting

 

5.13's are the way to go. I've never looked back!

 

Any comments on this post? I have 3.73 on a 12' sport and was contemplating 35's....but maybe not.

 

A completely broken-in 3.6L with auto, 35's, and 4.10's runs like a spotted ape. Do the searches.

Why anyone would recommend taller gears is completely unfounded. But the one common thing from all is that asthmatic 3.8L, not the 3.6L - apples and oranges.

Plus, you have to tell the computer, somehow, that the tire size has changed... and there are several ways to do that. I used AEV Procal, but there are other players too.

 

I have already ordered the 4.88. What would be the downside of them vs lower gear?

 

i put 5.13's in 3 weeks ago. shoould have done it as soon as i changed out my wheels.

 

^^^This. Anyone who keeps recommending 5.13's needs to realize that the 2012's with the new engine and tranny is a completely different setup, and doesn't need to be regeared nearly as low. Basically, the new 3.6 engine/auto tranny version of a 4.10 is the equivalent of the 3.8's version of a 4.88.


You'll be fine with any ratio of 4.10 to 4.88. Depending on what type of driving you do, it will either let the Jeep accelerate easier with the 4.88's, but lose a little MPG and rev higher at higher speeds. The 4.10's will not accelerate as easily as the 4.88's, but if you do a lot of highway driving, they would be better for not revving as high when you're going 75 mph.