Anyone that geared from 3.73 to 4.88s in a JKU auto with 35s? I'm looking to see what the highway (+70mph) mpg is. I hear that 5.13s are great, but the higher speed mpg gets killed because of the high rpm.

Thanks for your help fellas.

 

I would also like to know. I am leaning towards the 4.88 because I do a lot of highway driving.

 

I am getting ready to have gears changed in about a week. I am buying 4.88 based off a lot of comments by many other members. I have also based that off the chart that is given as an example when this topic comes up. According to the chart in the FAQ area an automatic with 35" tires and 4.88 gears will run at 2264 RPMs. If you go with 4.56 you be running 2115 RPM. From what everyone says your best MPG are when your right around 2100 RPMs. I will still go with 4.88s and expect to loose 1 - 2 MPGs solely based off the increase of tire size and weight. From what I read that is to be expected.

 

Good to hear. I'm thinking the same thing so I can't wait to hear how you like these gears. What company are you going with? G2, Yukon, etc ?

 

Hey Planman. I do appreciate your help, but I have reviewed every chart there is available. I have also read a lot about the 5.13s and I would love to have the power, but I don't want to be doing a 10 hour drive to Tahoe at 75mph in the +3k rpm range getting 8mpg. If this were a jeep made primarily for crawling, I would definitely go with 5.13s. But since I spend about 2 - 5 hours on the freeway just to get to the places that I like to offroad, I just think that 4.88s will be best. Besides, a supercharger is in the plan as well.

 

I have an 09 JKU with new front bumper and stinger, 3" lift , 35" MTZ tires etc and I went with 5.13 Yukon gears NOT 4.88 if you read more threads/ posts on this you will see more guys with this set up(sounds like the op set up too) you will see the guys will say 5.13 over 4.88...., I will add I never lost any mpg either..... using a superchip before and after the gears went in.

 

I don't come close to 3k rpm at that speed it's at 2500 rpm with a similar set up as yours.

 

I've desided to go with Yukon and I am going to buy the master overhaul kit along with the ring and pinion. Might as well swap out everything. JK only has 22,000 miles but I would rather have a complete matching set of guts rather than Mopar and Yukon mixed. Probably won't matter but I'm doing it anyway.

 

Can I ask what your average MPG is when on the highway? I mean around 70+ Not the 55mph highway. Thanks bud. I am still very unsure of what gears to go with.

 

Hmmm. After reading the post above you have me wondering. It is always a toss up. One guy says 4.88 and another 5.13

I'm not to worried about MPGs but at the same time I'm not saying I want to be back at 14MPG. My tires are actually 34.5" in Diamter. I do not usually drive over 70MPH. So based off what you are saying I would be much happier with the 5.13 when it comes to passing on the highway and it should not affect my MPGs to much?

This is one of those topics where there is a lot of pro and cons for either side.