section8JK

okay so I know this had been beating to death probably but I'd like to hear some other input on this, i have a 2013 JKU sport AUTO with 3.73's right now I'm running a 2.5 TF coil lift with some MTZ 33's. now i plan on going up to 35's here shortly just don't know which gear set to go with and the reason I'm asking is cause i can get a killer deal on a set of 5.13 but is it gonna be too much for my DD and bad on the highway? i go wheeling a good bit but just not sure i wanna go with such an aggressive gear since its more of a DD than a trail rig, thats why i also ask 4.88's or 4.56's?

aldaman

Below is a gearing chart that can help you decide. Most advertised 35" tires actually measure out between 33.75" - 34" so that is the size you would go by when reading the chart. I currently am running 35" tires with 4.10 gearing on my JK with an auto trans. For my JKU-R it runs fine unweighted (stock bumpers) but eventually when I regear, I will be going with 4.88. The reason for that is, it is suitable for my syle of driving and terrain. Plus I don't offroad very much and with the Rubi T case that gearing should suffice. If I did a lot of off-roading and going up to 37s then maybe I would go with 5.13s.



aldaman

section8JK

first time i've seen that chart only one i could ever find was the one for the 3.8's but thanks that helps a lot maybe if were to go with 37's with the 5.13's it would be better but not looking to drop that much on tires again thats a nightmare gonna try to stay with 35's thanks a lot

aldaman

Yup, if you stick with 35" tires based on the chart, a true 35" tire will only put your RPM at 2700+ at 70mph which would be perfect IMO....

This gearing will give you the torque/get up and go you need and for your DD your RPMs won't be over 3k....

eschber

In addition to gearing, you should also consider the additional strain on other components that bigger tires puts on on the vehicle. A larger diameter tire means more leverage. Think about a steering wheel on an 18 wheeler vs. a go cart. Bigger tires means you increase the chance of breaking an axle or drive shaft. There is also more wear and tear on brakes. All things to consider when looking at bigger tires. I know the front diff and T case is different in the Rubi vs. sport JKs but I don't believe they have the same axle shafts. Please correct me if I'm wrong.

Sahara Lee

I ran 35's (315/70R17 Duratracs) on my JKUS (3.8L (1 gallon)) for the past 6 months with stock 3.73 gears. It really wasn't that bad. Even on highway at 70mph it stayed in OD here in flat Florida.

That said, after the holidays I'm changing to 4.88 just to add a little low gear torque. Also putting in Detroit Locker TrueTracs front and rear while I have them apart.

Your 3.6 is geared lower than my 3.8 to start with. To turn the same RPM at 70mph as your Pentastar with 3.73 gears I would have to have 4.49 gears.

You should be good with 3.73 gears. If you find it's too sluggish you can always change them later.

Jeepstin12

im running the stock Rubi 4:10's with 35's. Runs good. Drive frequently in the Colorado mountains. I may go to 4:56's.......eventually, maybe, but don't feel the need to.

tljk2007

I have 2 2013 jk's. One 6 speed with 5:13's on 35's and a jku auto with 4:10's and 35's. I thought the 4:10 was great until I drove the one with 5:13's for a while. Its getting about 2 mpg better mileage(I know it don't make since to me either but that is what I'm seeing) and there is no down shifting on hills. If you do alot of hwy driving at 75 to 80 mph, you might want to try 4:88 but I'm a lot happier with the 5:13 than the 4:10. I will probably drop to 33's on the jku since its more my wife's than mine now.

Idaho 51

Did you say your was an Auto? I have the stock tires, still, and the Auto shifts like crazy, on the hills, I15 in Utah is above 6000' and 75 & 80 mph.

Idaho 51

2 mpg better, better than what? yours is a '13 though.