Had 4.56's in my 12 jku. Perfect gear setup for my needs. I crawled in big bear, and daily drove up and down the 5, 405, 73 ect.. when I lived in orange county.

 

I have a rubicon

 

Interesting thread as I am in a similar position. Have a 2013 JKU auto w/ 3.73. I put 315/70r17 tires on. I would like just alittle more on the highway. According to the charts, 4.10 gets me back to 3.73 performance. Some say put alittle extra gear in to compensate for the additional weight of bumpers, gears and aerodynamic drag (lift). I run lift, front & rear bumpers, steps, spare tire.

I have read that if you put the jeep in 4th gear (auto) on 2012+ years, that would be the equivelant of 4.56 gears, if you really have 3.73. This would give you an idea of RPM at 70 mph.

 

The easy way to think about it is that you need more horsepower to move a heavier rig with larger tires. Getting back to stock rpm on a larger tire and heavier rig, doesn't cut it. You need to be higher up in the RPM range where more horsepower is made.

Paying to go to 4.10 on a 2012+ makes no sense if you run 34"-35" tires. Also, it is a misconception that higher rpm means lower mpg. The goal is maximizing efficiency. At 4.56, the average use case will downshift less, thereby increasing fuel economy.

I went from 3.73 on a light 2013 2 door, to 4.88. On my 35s it actually was pretty nice, but 4.56 would have been ideal if I did a lot of highway. I went to 37s, which is why 4.88 made sense.

The new engines run great in the mid 2000's.

 

What about 4.10 six speed with 37's

 

I would do 4.56 or 4.88.........................

 

.............................

 

Definitely 4.88... If I were going to choose between 4.10 and 4.56 it would be 4.56 but I love the 35/4.88 combo in mine and I daily drive. Just don't under gear.

 

You won't use your higher gears...

 

I have 07 with 4.10 32" tires