Since there are always a ton of questions here about "what gears should" I thought I would post a bit of feedback about mysetup and experience.

2013 JKU, 3.6L automatic , 34" Duratracs

I had 3.73 gears in it to start. It was OK, but struggled a bit at freeway speeds if there was any wind at all, or hilly for that matter. I could have definately "gotten by", but decided to take the plunge and regear.
I spent endless hours reading about others expeience and flip flopped between 4.10s and 4.56s for months. Finally I decided on 4.56s. If nothing else, it would future proof me, should I want to go with 37s at some point. We ordered up the parts and a guy swapped them for me at the end of last week.

Initial observations:

The driveability is SOOOOO much better. Way more responsive in town and no longer downshifts on hills or windy conditions. I would give it a 10 for a fun factor.
So far, the fuel mileage increased for city driving. Just watching the guage on the dash, which at least in my case has proven to be quite accurate, is showing about 16mpg in town. That is about 1-2 mpg better than before.
On the highway unfortunately it appears that it is much worse. Seems to be holding steady in the low 15s at freeway speeds ( 70-80mpg). The interesting thing is that it does not seem to matter much if I am running at 65mph or 80 mph, which is a good thing. Again, this is just a couple of days of observations. Over the next few weeks, I will hand calculate the mileage.


RPMs with the 3.73s were about 2300rpm @ 70mph
RPMS with the 4.56s were about 2800rpm @ 70mph

Was the 4.56 the right choice? Not sure yet. It appears the 4.10s probably would have done better in the MPG arena, but lets face it, the MPG on these things suck pretty bad in general so may as well enjoy it

 

My Experience:

12 JKU auto
Daily driver
35" nittos trial grapplers

4.10s are good for DD and drive-ability is what i consider normal with good acceleration etc.. Highway driving is very good and doesn't down shift often when cruising on the highway at 70MPH.

It hauls a trailer OK but 4.56 would be better.

MPG based upon dash gauge.
Highway MPG -16 at 70MPH
City MPG - 13-15

if i have to do gears again it will be 4.56.

 

I have a 2014 regeared to 4.56 also. Used the AEV procal to reset speedo. I like my choice.

 

Northlander this is one of the more helpful threads I've read in a while. Thanks for sharing!

 

Upgraded from 3.21s to 4.88s and do not regret it a single bit. Don't care about MPG and running 35s.

 

Glad I could help. I actually traded mine in on a new Rubcicon yesterday. Tuesday I pick it up and will get a good comparison of the same setup with 4.10s in the new one. I am retaining all my tires/wheels. bumpers etc which will get bolted on the new one. Hope the 4.10s work out OK. I very much likes the 4.56s.

 

Awesome thread as much as it seems to switch to 4.56 I'm only goin to run 33's and dd so I'm def going to go with 4.10 big question can I just buy said 4.10 good gears and pay someone to drop them in? Or need something more. 2013 oscar mike jku 3.21 gears

Sent from my dogs cell phone

 

Running 37's with 4.56's and auto.

Couldn't be happier.

The RPM on the highway is about 2550 at 70 and in town good pull and drive-ability.

I don't look at MPG, it is a brick with wheels.

 

You are going to need a new front carrier, so you might want to look into either truetracs or a locker as they are carriers.

 

I went with 4.88 gears on a 6 speed manual and eventually changed them back to 4.56. I have a post on it somewhere in this forum. 4.56 seems to be great though and I'm really, really happy with it.