I know this topic has been beat to death, however, lets get specific. I have a 2dr automatic Rubicon, I live in Montana so it's hilly to say the least, and I'm running a 3.5" lift with 35's and Superchips Flashpac. I definitly need gears so it's either 4.88 or 5.13. Right now at 70 mph I'm tacking about 18-1900 rpm's and I do run a lot of highway miles.

All you super experienced JKers out there put your two cents in as to which ratio you would reccomend for my circumstances. The AEV guys here in Missoula claim 4.88's are plenty, but it seems most Jeep's end up with 5.13's.

I have looked at the gear ratio chart, but I'm looking for real world experience to guide me in my decision. Thanks for any advice

 

I've always wondered about AEVs 4.88 for auto/35 recommendation. I guess they think the extra rpms are enough. If they are enough to keep you from shifting out of OD a lot, then I'd imagine they'd give you better mpg than 5.13s if you're on the highway a lot.

Seems like every post on here from guys running 4.88s is that they wished that they got 5.13s.

I'm trusting the 5.13 crowd, I just got a set from Northridge4x4 and am waiting for an appt to get them installed.

 

I have a auto 4dr with 35s, (more like 34's now) and got 5.13s and its great on the highway, cant keep speed in OD now without all the downshifting and the low end power around town is back. gas mileage is pretty much the same as before when I had 3.73s. It does rev a little high on the highway, and I think when I go to 37's it will be perfect.

 

I was wondering about that recommendation too. I think they are better for an automatic with their Hemi conversion which would be nice, but won't be happening anytime soon for me. I am leaning toward 5.13's, but I have a tendancy to research and over think things to death before I make a final decision.

 

I researched for a year, and I went with 5.13s. I was too at a cross road with the 4.88 and 5.13 choice. With everyone that has autos and 35's or bigger and doing fine, seemed like the best route to go. I'm getting mine installed this weekend!

 

Thanks for responding to my PM I sent you .... I sent you a thank you PM but it said your box was full and can't except any more PM's until you create space.
Thanks again.

 

I think 4.88s are a big mistake, and 5.13s are not low enough. I had 5.38s in a two door rubi, auto, with 35s, and thought it was about perfect. On flat ground and modest hills the transmission will stay in OD, provided there is not too much of a headwind. On any reasonable grade, or with anything other than a minor headwind, your still going to be in third gear frequently. But at least you wont be down in second gear very often. The 5.38s do a good job of keeping your trans from shifting all the way down to second gear.

 

I have a 4 door w/3.5" lift and 35's and put 5.13's in a few months ago, and I couldn't be happier. I live in Reno and drive over passes every weekend to ski, now I can drive at a respectable RPM in 3rd gear, instead of screaming along in 2nd gear. I'm at 2500 rpm at 70 mph in OD on the highway and rarely downshift into 3rd. My MPG's actually went up due to utilizing OD on the freeway (use to always downshift into 3rd on the hwy) and not using 2nd all the time going over passes.

 

Sounds like 5.13 is the way to go. Thanks

 

Hmmmmm. 5.38's huh? So far even with the stock 4.10's and 35's my trans has never shifted down to second even with Montana grades and wind. The idea of no downshifts is very appealing, but 5.38 scares me a little. What kind of rpm's were you running at around 70 mph?