When I started my mods, I “knew”that I would “never” go above 35” tires.
2017 JKUR 3.6 auto transmission
Anyway I re-geared to 4:56.
At the time I was daily driving it, I do a lot of highway driving and tend to run 75 when the limit is 70.
Skip ahead a few good wheeling trips.
My old 2000 F250 4x4 7.3 needed tires. I said to myself this is a perfect time to put 37s on the JK, the 35” Nittos still had a ton of life in them, they went on the truck and I put 37s on the Jeep assuming that I’d need to stash some cash to make the jump to 4:88s
What I ultimately found, and was pleased about is.
At highway speeds 55- (cringe)80, my RPMs dropped just enough that the JK didn’t seem to be wound up as much.
These are close but not exact numbers.
4:56 @ 80 MPH = 2950-3000 RPMs (35” Nitto Trail grapplers.)
With the 37” Trail Grapplers I’m running closer to 2750-2850 RPMs @ 80mph. (Again I cringe) I don’t like to think about running that fast but frequently find myself doing so on Texas Highways with low traffic in the area.
I found no significant drop in fuel mileage, I’m sure it dropped some but it wasn’t huge and my wallet didn’t feel it. If it was significant my wallet would have noticed because it’s hungry all the time.
The best part was, I noticed no drop off in (off road) performance. I wheel exclusively in 4Lo.
I’m guessing the difference would be more noticed in 4hi if I used that.
Bottom line is, I’m personally (perfectly)happy with the 4:56s and the Nitto 37s. I’m mentioning “Nitto” because they do run closer to 36” mounted and aired up. Other brands may run truer to size, an actual 37” tall tire may have different end results.
I’m away from home at the moment, and in my truck. I’ll try to make a little video for you (on road) when I get home.
I also have reset all parameters with SuperChips tuner. My rig shifts flawlessly.
Last edited by Pmedic920; 01-21-2020 at 09:29 AM.