I'm thinking about re gearing my 09 Unlimited. I'm thinking of going up to a 5.13 in the front dana 30 & 5.38 in the rear dana 44. I've been told numerous things ... if I go up in gear ratio from stock (i'm running 37" tires) I will get some power back & my gas mileage will increase. I've also been told I will get some power back but my gas mileage will decrease. I'm currently getting anywhere from 12 - 12.8 mpg & my JK is my daily driver. Any help would be greatly appreciated, I'm not trying to make the wrong decision.

 

You have to do the same gear size front and rear

 

"I'm thinking about re gearing my 09 Unlimited. I'm thinking of going up to a 5.13 in the front dana 30 & 5.38 in the rear dana 44."

You have to use the same gear size front and rear. Your limiting factor is the Dana 30, so the lowest gear you can use is the 5.13.

 

Do report back as to how you like the effect of non-matching ratios front and rear.

 

Yea, I'd like to see what happens too!!!! Not matching the ratios will be fun to watch!!!!!!
Make sure to take allot of pics of the carnage!!!!

 

ditto - you'll be chirping on the trails with 2 different gear ratios!


if you get tall, narrow, non-aggressive tread you may get better gas mileage but don't go re-gearing and changing and getting larger tires to get better gas mileage.

 

not sure why he's getting 12MPG stock??? i used to get 17-20 stock. i even get 14/15MPG with Mickey THompson MUD tires.

 

thanks for the info ... people i asked told me I could do different ratios front & rear. What about my mpg? will it increase or decrease?

 

My mileage increased about 3 mpgs after I went from 4.10s to 5.13s, with 35s and a Superchip 87 tune. My JK drives better now than it did bone stock. The othre bonus is you take a lot of increased strain off of the drivetrain system as a whole with new gears.

This is a good link for questions and info...

https://www.jk-forum.com/forums/jk-write-ups-39/gearing-82262/

 

THANK YOU!

I'll keep you updated