I know there are similar threads - but searching them I haven't found a good answer. I have a 2013 Rubi JKU automatic with 3.73 gears. I have a bumper, winch, 2.5 RE lift and 35s on the way. I know I'm going to need to regear in the future, but I'm wondering if anyone is running this or a similar set up (with the 3.6 VVT engine). I'm trying to get an idea as to how much the 35s will turn my jku into a slug with the 3.73 gearing. Thanks

 

You should be fine. I'm running my '12 4dr rubi with a 2.5" lift, 4.10s auto trans and 37's no problem. In fact without the top and doors on the tires will chirp accelerating off the line fast

 

U might be surprised that is what I'm running and I didn't lose as much power as I thought. I'm running KM2's

Sent from my DROID BIONIC using JK-Forum

 

With 35's you should be okay, but go any bigger and you're going to want to regear. Even with 4.10s and the 3.6L, most people are regearing to at least 4.88s. I have the slug-ass minivan mill and went to 5.13s. Much better than the stock 4.10s, but if I had it to do over again, I'd probably have regeared to 5.38s.

Just try it with 3.73s and if you end up not liking it, regear. Doesn't have to be done immediately. I ran 37's and 4.10s with the 3.8L for well over a year as a daily driver.

 

I have the same set-up on a 3.8 which has "less power" and I live in the mountains. As long as I turn off the o/d I'm good. I also have f/r bumpers 5" lift, sliders.

 

Ok - that makes me feel a little better. Thanks for the input. Much appreciated

 

gearing on the 2012+ seems to be more of a personal prefrence in driving styles. I am running 3.73 w/ 35's and have no plans to regear. I can still get 17mpg highway from dallas-san antonio going 75mpg with some hills, about 18mpg going 75mph to and from houston and even up to 19mpg going to bridgeport which is only 65mphs and pretty flat.

From what I have read, if you are the kind of person who likes to gun it a lot and drive pretty fast you can get better city MPG with new gears but you will lose out on the top end when you are cruising at higher speeds. I still get 13-14 in the city which isn't too far off from what I was getting with 32's.

So gearing will be dependant on what you are looking for... if you want your engine under less load as you gun around town then you might decide to get more agressive gears. I just drove mine around town for about a year now with 35's and I don't feel like I have any problems getting up to highway speeds and getting around in traffic and I am not willing to take the hit on highway milage I have seen people say they get with going to 4.56... I guess 4.10 would be a nice happy middle ground but to me its not worth the cost of regearing for such a small bump.

 

None at all if you reprogram the transmission shift points with procal or something equivalent. The shift point calibration is a big deal for drivability in my view, make sure you use the measured while mounted on the vehicle tire size.

Remember with 3.73s and 35s you are still geared lower than a stock 3.21 with 31 s, switching between my buddies 3.21 /31 tired 13 Sahara and my 2013 with 3.73's and 34s mine drives better- better accel, better trans choices through the gears. Both Unlimiteds w/hardtops. On road I doubt you would need more gear. Off road it is going to be the type of driving you do. With autos you can get away with less gear , torque converter makes up for some of it. Low range is deep in the 241, 2.72, and the OR case with 4:1 even more so, so it will come down to trails you run or don't run....

The 3.6 L does a great job pushing these beasts, much, much better than the 3.8 in the past. The whole powertrain counts, and the computer controlling the fuel trims and the trans shift points etc , has to have the correct inputs.

 

I have a 2.5” lift on a 2012 automatic with 35” Dura tracks and it is fine. The only problem I could see, with the cruse control set at 70 it sometimes will take time to move into 5th gear. All you have to do is hit the shifter to the right and manually shift into 5th. The same goes for step hills but drop down to a lower gear by pushing the gear shifter to the left. I would never spend the money to re-gear after seeing what its like.

 

What gears do you have? I also have a 2012 automatic with a 2.5" lift and am looking into tires. The reason I am asking is I have 4:10 gears and wonder if you have 3:73 so need to do some manual shifting. Can't decide between 35's or 315.