Next time you approach a hill on the hiway, hit the O/D Off button just before you start up the hill. That will give you an idea what a small re-gear will be like in that situation.

 

Yes it will certainly help on highway. Ideal gearing will put you in a better rpm range on highway and less downshifting. Just don't over do it or mpg will suffer. What size tires do you have and what are future tire size plans

 

Yes it will certainly help on highway. Ideal gearing will put you in a better rpm range on highway and less downshifting. Just don't over do it or mpg will suffer. What size tires do you have and what are future tire size plans[/QUOTE]

I have 35's don't plan on changing any time soon, they're brand new. What kind of gas mileage are u guys with tuners, automatics and 35's getting on highway, I only get about 13-13.5

 

No help there lol. 2012, manual, 3.21's, 35's, no programmer, 14-18 mpg (15 avg based on the dash, but that's technically low based on speedo being off).

 

I was running 35's with stock 4:10's....sucked on interstate. Added a Hypertech tuner. Helped keep it from downshifting a little bit. Jeep still wouldn't hold speed on flat interstate. Instead of shifting very mile it was maybe every 5-7 miles.
Went to 5:38's and 37's, wow, feels like it did with the stock tires. Runs at 2400 RPM at 70.
Seems to be the sweet spot for the 3.8.
Actually goes up some hills even without shifting.
Mileage before gearing was 13-15 interstate. Now even with 37 mud grapplers I can squeeze 17 on interstate. Around town I was getting 14.7 when I did the math on yesterday's fill up.

 

And those gears are still good for wheeling because I don't want to lose any low end torque

 

Oh yeah. Makes wheeling better. Gives it more torque in 4lo. I have to hold the brake now in drive or else it starts crawling away.
It didn't do that with the 4:10's. Always had to gas it to get it to go with the 4:10's.

 

Sorry for the stupid questions, never regeared anything before but now that I'm driving more on the highway I can't stand it lol, so if I regear it'll make low speed and high speed driving better? I just always thought it would improve one and not the other

 

If you regear properly based on tire size and your driving habits/ uses, crawling and highway performance will improve. If you get too low of a gear (numerically higher such as 5.38), your crawling will be amazing, but RPM's on highway will be too high and MPG suffers. Finding the perfect median is the key.

 

Hmmm... Well, my point wasn't that I want to do "burn outs", but seeing my JK has 3.21 and a 6 speed... I felt a big difference when I added the 33's, just didn't seem to have as much get up and go... So after the Diablo... I now have better power.

I mostly run back roads (50-55mph and 4th gear) and now getting over 17mph. Not sure what my highway mpg is like, but when I do drive the highway I have good power to past semi's and if I need too, dropping to 5th always helps.

Bottom line... I thought my tuner was well worth it.

I too, would like to go to 4.10/4.56's and 35's... After these 33's are wore out. Better yet, if my pockets get deeper, I would an LS instead of this 3.8. (nice to dream I guess)

Just my 2 cents anyway.