I had the same set up as you. I went to 5:13's and it was the best thing I ever did, IMO. Gas mileage is anywhere a between 14 - 17 mpg depending upon how, and where, I'm driving.

 

True story, ... 1/2 a tank of gas burned in 50 miles, uphill, into a headwind. How long would it take for new gears to pay for themselves?

 

No I was telling someone how ya said to either stay 4.10 with OD off or goto 5.13.

 

Well, 87 octane is about $3.39\gal in my area, so not too long at 5mpg

I'd be more concerned with popping the motor at sustained high RPM's for that distance on a regular basis.

 

This is the problem with my Auto Rubi. I'm running 35s, but even when it was stock it would do this in the mountains with OD-Off. Regearing next month to either 5.13s or 5.38s.

 

I have a Rubicon with 4.10 gears but I thought it would be worthwhile to pass on my experiences with 35" tires.

Like just about everyone else, I was surprised at how much of a dog the JK automatic was, especially on the highway and on hills. I figured I'd need to re-gear ASAP once I installed my Duratrac 35" tires.

However, I've had the tires on for a couple of months now (covering about 2,000 miles both on and off-road) and I'm still running my stock gears. I haven't really felt much of a difference in driveability on surface streets. The Jeep downshifted out of overdrive all the time on hills with stock tires and it does it even more now (and there are a lot of hills on San Diego). It dips down to second gear upon occasion as well (depending on how much I'm hoofing it). I didn't really notice any difference when off-road.

Most of my driving is on surface streets. My mileage was bad with stock tires (12 or so) and it's bad with 35" tires (11 or so). I've done some experimenting on highway trips and if it's flat and I can leave the transmission in overdrive I get somewhere around 16-18 MPG (which is about what I got stock). If it's hilly I turn the overdrive off and the MPG drops to 15 or so.

So, all in all, for my driving, it's not nearly as bad as I expected. I'm going to do more mileage runs and then make my final decision but I'm not rushing out to spend $1,000 on gears at this point. With the mileage difference I'm getting, I'd have to put on something like 20,000 miles to break even on the gears.

As always, you mileage may vary!

 

I'm in North San Diego County and probably drive the same roads as you. My MPG is about 11mpg (city) with KM2 35's before I flashed with an aftermarket programmer. With stock 4:10's and KM2 35's, going up\ down the I-15 or I-5 was just 'ok' and the flash seemed to make stock gearing better. I'm regearing anyways, but not for better MPG.

 

If I was on the freeway more I'm sure it would make much more of a difference. I'm a leadfoot too so my mileage tends to be on the low end of the scale for any given vehicle.

I forgot to mention that I do have a AeV ProCal and have adjusted the computer for the correct tire size.

 

I know what you mean, my JK is not my DD, I have an F150 and motorcycles (crotch rocket and dual sport) for that. So, I don't do much freeway driving either.

 

I can't wait for the salty roads disappear in March, I recently installed a lift and 35 MTRs so I'm chomping at the bit to see how stock 4.10's are. I have a trip planned in July for Deadwood so I wanna decide before than to regear or not. Since it's not a DD I am thinking 5.13