I currently have a 07 auto jku with 35s. The jeep does fine with no hills but when I go to Colorado a 12 hr trip for me all I can say is its miserable and I am afraid the thing is going to blow up lol. I have regeared to 5.13s and it did help with acceleration but on hills it still wants to hunt gears. If I never wanted to run bigger than 37s would the 3.6 be a good option or should I wait and see what the next generation brings. I just want to be able to run 75-80 on cruise without major problems. I have also looked into an LS and it would be a more expensive option.

Sorry if this has been covered. I have been inactive for a while since I got my jeep where I want it.

 

So I'm on 37s with a 3.6 auto and 4.56s. I love it. Personally, I'll wait a year after the new wrangler comes out to ensure they get kinks sorted out.

 

I'm on 37" with a 2014 3.6L and 4.88 gears, I cruise on the interstate at 65 mph for the sake of fuel, I can get 13.5 mpg at 65. If I try to go 70 or 75, that number keeps dropping. I don't like buying gas. Around town I get 15-15.5 mpg.
I have no power issues or any issues dropping away from OD on the interstates.

 

Have you used a superchips or AEV procal to account for the 37s? I had 37s on my last jeep for 4 years and never did it, have 37s on my current jeep and just did it at 7k miles and it's night and day. I can cruise at 75 without any hiccups, the new shift points after accounting for the 37s is a game Changer. It gave all the drive ability back to the jeep and I'm currently getting 17+mpg highway. I'll regear at somepoint but even the AEV procal made a huge difference

 

If your asking me about that, yes, I have a Superchips FlashCal F5 set to 4.88 gears and 36.5" tires. The Jeep couldn't be moved out of the garage without it, I tried to back it out of the garage bay and it went into limp mode and lit the dash up like a Christmas tree. So I installed the corrections, and BOOM! MONEY! It drives like stock and all is well in the world. But the fuel economy is way lower, I GPS verified the speedometer, its off 1 MPH at 65 indicated. GPS shows 64. I also hand calculate the fuel economy every tank, and the DIC is only off about a half of a MPG. It would be nice to be able to go 75 and get 17 MPG! I'm going on a 3500 mile round trip in July to Ouray Co. I may air it way up and see if that helps on the super slab.

 

I have 4.56's and 37's I'm getting 17 mpg on highway and 15.6mpg in the city stop and go. I think it's a good middle ground setup for gears.

 

If you have to run steep grades I would not go over 35's with the 3.8 auto. That set up just sucks. I run 5.13 with the 6 speed on 40's and it is the same thing. Drop to 4th gear to get up the hill.

 

I'm a 2011 jk manual 6 speed with 4.88s on 37s Nitto mud grapplers on a 4.5 aev lift. If I drop to 5th gear, I can hit over 100mph. A bit sketchy but had my axles reinforced. I have a 3.8 with over 100k miles on but she still runs strong. No engine upgrades other than a redrock snorkel. I'll send in pics next time cause I know there will be people saying I'm lying.

 

100+ MPH in a Jeep on 37's!!! Your the man!! I'm guessing you used a TomTom or other GPS unit to track speed since the speedo was buried. My tires are only rated for 90MPH just enough to activate my Flux compasitor but I'm sure they won't spontaisly combust at 90. I think I'v hit 90 once on the Jersy T-Pike.

 

Upgraded my flash cal to a flash pac. Compensated the gears, tires, and psi. Speedo all set.