I have a quick gear question and break down of what my rationale is. Let me know what you all think in regards to what gears I should run.

Jeep Info:
- '13 JKU and looking at running 315/70R17 Nitto Trail Grapplers on. As most know the Nittos are heavier.
- I don't see myself running 37s anytime soon. However, if I run the Nitto Trails in 35 or 315/70 they are a heavier tire as mentioned.
- As far as weight, I hope to get a front and rear bumper and winch sometime in the, hopefully, not too distant future. I currently have the Rubi rail and Ace sliders.
- my JKU currently has the 3:73's
- terrain around here isn't mountainous or very hilly. More mud than anything.

Rationale:
I had 4:56 in my Tahoe with 6" lift and 35s years ago along with a programmer and it seemed to do alright. Although the jeep is going to have less horsepower (don't know that that matters much). I'm thinking that I would not really be able to tell the difference between 4:56 and 4:88 as far as daily driving goes, mpg, etc., etc. So that makes me think that maybe I should just go the 4:88 route. My only hold back of just going 4:88 is due to the fact that my rig sees mostly pavement and a good mix of highway/city, maybe more highway than some. I have to drive interstate everyday for work. Not long distance though.

Are my comments on not being able to really know the difference between the 4:56 and 4:88 sound about right? OR is my normal day to day driving habits sound like I need to stick with 4:56?

Thanks.

 

Auto or manual?

 

We are almost the same except I have 4.56's and I geared it for 37's.... soon.

For 35's in the Nitto's I recommend 4.10's as an all around gear.

But for off road and in town driving the 4.56's can not be beat.

RPM is a little high on the interstate but not so I care.

 

Auto transmission. The chart you posted is a little different that another one I looked at. This one has everything geared lower (numerically higher numbers) than the other chart I reviewed. Interesting...

 

The charts for 3.8 and 3.6 are different.

 

I just noticed that on the chart that was posted. The one I had previously looked at put 4:56 right in the middle for 35s.

 

The difference on the highway is less than 200 engine rpm. It will make virtually no difference in mpg or engine longevity.

However, 4.88s will be better off road, and the mpg should be better for in town mpg.

Unless your daily commute is long at 75-80 mph, 4.56s don't make any sense. (They cost more than 4.88s.)

Do you have a long daily commute at over 75 mph?

Does less than 200 extra rpm bother you?

 

You also need to know that the chart is based on actual, mounted and under the jeep tire size.

Most 35s measure closer to 34s.

 

Oops my bad. Yes the chart I posted is for 3.8 I see you have a 3.6

I'd go with 4.88s. And as Planman said most 35's are actually closer to 34"

 

I'm running 315 duratracs which measure out to 33.75"
I'm running 4:56 gears with a manual Trans.
It's my DD and toy.
I think the 4:56's are the perfect gear for my setup.
I can start off in first without giving it gas, but it's also manageable at 70 mph.
I'm getting the same mpg I got with 32's and 3:73's