UnJKlimited

I used Flashcal to program for tires and gears. Amazon has it for 150 bucks with free shipping.

planman

A Flashpac is a tuner with significantly greater capabilities than a calibrator, like a ProCal.

You should be able to pic up at least 1 mpg from a Flashpac tune, while increasing your engine performance.

achtung

I have a 2013 RUBI 6spd 4.10 and will do 4.88 with 35" and then later get 37" tires. and then maybe back to 35". i will have the big front and rear bumpers and the later the big rack. so i feel that the 4.88 will be just fine. no matter what tires i have on.
or am i going wrong with that vision?

Bob Mroz

I have a 2012 6speed came with 3.21 gears. 33 tires. Old set up was 2500 rpms in 5th 73 mph 6th was useless unless above 80 !! New set up 4.10 gears now 6th gear is 2500rpm at 72 mph. I was on the fence with 4.56. Glad I went with 4.10. Honestly I think these gears would be ok with 35's

rodi

Do you know what RPM you are running at 70mph? I have 285 duratracs and 3.73 and was contemplating regearing with the 315s. I have 6-spd as well. I also thought about getting a 4-speed atlas and keeping the 3.73 gears for highway travel.

rodi

Also, while low engine speed at 70 is good for mileage, if you have to mash the gas too much it's a waste, compared to a lower gear and less gas mashing and only slightly higher engine speed at 70.

Stuka

There is certainly a big difference between 3.8L and 3.6L JK's. My '08 with 4.56's and 33's (With a 6sp) is perfect. I am almost not sure if I want to go up to 35's because the gearing will be less optimal.

Softtailfreek

I have a 2012 with a six speed, 35's and 3.73 and have no issues running down the road at highway speeds in 6th gear. I don't really see the need to regear with this setup unless your off road a lot. Btw getting 15.8 mpg running around town and 16.5 highway

blue_chaser

6th gear
50 mph, 1450 rpm
60 mph, 1800 rpm
70 mph, 2100 rpm 18+ mpg
Speed confirmed with GPS. I swapped my TC with Robbie in LV for $500 and paid $230 to have it installed. Another $75 or so for freight to return my TC to him. Atlas would have been nice but 3x the cost.

jkfletch7

I'm not sure if anybody said this but there is a simple formula to get the gearing that you want... ((Tire size you have)x(stock gear ratio you want to match)) / (stock tire size) = gear ratio you want

Also you want to round up to the nearest gear size to offset the increased weight