Would my gas mileage get better going form 31’s to 33’s? I currently run 31’s and my door jam code tells me I have 4.88’s in my 3.0 Auto. I have looked at gear ratio/rpm charts and with 4.88’s the fuel economy seems to get better. Am I reading the chart wrong or what? I have searched and could only find what people suggested the gear ration should be, but none about gears and gas mileage. Thanks in advance.

 

You're already undergeared, and it will get a lot worse with 33's.

Those charts generally assume you have a powerful motor and that it will pull the gear at the new RPM. Our trucks won't - you need to be at least one ratio lower than those charts recommend, and for an auto, I would go two ratios. That will keep your RPM's on the low end of the power band so you can hold the overdrive and not be flooring it at every rise in the road.

Yes, that means you're looking at 5.71's for 33's with an auto tranny ...

 

Thanks for the quick response. Well, looks like I'm taking the other route I've read about, and go out and get the locker and keep the 31's instead of getting 33's and regearing with no locker ...... How does your 93 3.0 run with 33x10.50's? I assume it's stick but is it bad?

 

Good decision. 31's with a locker will outwheel 33's open EVERY time. I would save up and do gears and lockers at the same time.

Mine is a stick with 4.88's and it does OK, even here at altitude. With the 4.56's, it lost all (Ok, whatever it had) it's "pep" on the freeway. Amazing what a difference a couple hundred RPM make with these engines...

Molly's is an auto with 35's and 5.71's and it's a DOG.

 

I wouldn't have thought that there would be that much difference between the 4Runners and the trucks.

 

I noticed a small drop in MPG right after putting the 33's on. After a tune-up, seafoam, Aisin swap and ISR mod it's pretty close to what it was before. So it was probably not the best to begin with, but for me that's OK because I didn't lose any MPG that I started with. Running 4.88's with 33's seems to have no reduced performance in city/highway driving but my tranny was just replaced not too long ago so I'm sure that helped. I suppose you don't want to trade your locker for my 33's

 

Ha no trades here! good try though! yea gears and locker at the same time would be good that way they only have to go in there one time. I think that's the answer then. Stick with 31's until either A) i can get regeared or B) Gas becomes less than $0.50 a gallon and slow speeds don't bother me. Looks by summer time i should be locked with possibly new gears! how would 5.71s do with 31's for a while?

 

would this be all i need for the gears?

http://www.4wheelparts.com/PDT291694.aspx

 

Bigger tires will hurt mpg, more drag and mass.

You'd need 5.71's with 33's and the auto tranny. I have the 4.88/31" tire combo and your truck is perfect with the 31's. In fact it came from the factory that way.

Frank