Trying to decide if I should switch out the gears on my 09 JK, drive about 60 miles a day to work. It is not sluggish with all the mods that I have done so far, but the mpg just keeps tanking, getting close to single digits on the highway. Also have a lot of gear searching. Any help would be greatly appreciated.

 

I drive about 40 miles a day and swapped my 3.73's to 4.56. I have a 2010 2dr w/ auto trans. I have heavy bumpers, tires and skids. My average mpg's is now 15.8 - 16.2. I also run the superchips 93 tune for a little extra power.

 

What size tire are you running? What size will you go up to?

Sent from my SAMSUNG-SGH-I317 using JK-Forum

 

x2,
Give us some more info - tire size and is it an auto or manual. Properly gearing to tire size and vehicle weight makes a huge improvement in fuel economy and power.

 

It is an auto, currently running 35's might be going to 37's

 

3.8, 4door, auto, 35's, going to 37's.

You want 5.13's.
If a front d44/d60 is in your future, consider 5.38's.

Open the faq's at the top of this modified area. Scroll down to the drivetrain section. Plug some numbers into the chart. (use measured tire height, not mfg spec. If you want OD Off rpm, just divide the number you get by .69)

 

At a minimum I would go 4.88 for 35's and one set higher than those for 37's. Depending on your needs you could go two sets higher. I personally wouldn't go near 37's and drive 60 miles a day. That is going to wear on so many other parts and cost a lot when they all have to be replaced. Not saying 35's won't either but they are more practical. I run 34's and they work perfectly for me.

 

Thanks, found that FAQ's Sticky after I posted.

 

Cannot find the Drivetrain Section. Do you have to be a registered user?

 

Im running 37s with 40s on order. Im running 4.10s and im getting 14.5 on the highway and 12 around town. I have a superchip and it helped it a ton. Personally if i were you try a superchip that will probably solve your problem. Mines also a auto trans