So i did some research online to find what gears i had. The sticker on the door reads "G254", which i found to mean 8" ring 4.56 ratio. However, i marked the tire and the drive shaft, and found that the drive shaft spins roughly 2.25 times to every one tire revolution. that ratio seems inaccurate. The vehicle is a '92 4runner with 3.0 and manual trans. any info would be great.

 

gotcha, so the sticker was correct? what ratio would work the best for 33's on that vehicle with that engine 4.88's?

 

ive had the 33s on there (currently), it too seems a little sluggish on the highway. i find myself shifting from 4th to 5th and back again to hold 65 to 70 mph. if i move to 4.88s do you think rpms would be higher than desired, and poor gas milage?

 

You'll find that your engine will struggle alot less to turn the larger and heavier tires.
And in my opinion, my MPG's went up when i went from 4.10 to 4.30..
And i'm only on 30" tires, but bumping up to 33's soon.

 

No, it doesn't really make sense.

The math is right, but the wording isn't. The word "axle" is misused, and the term "twice as fast" is a misrepresentation of the facts.

The "axle", or to use the proper terminology, the ring gear/carrier will actually spin 1/2 as fast. That's why it requires 2 full wheel/tire(axleshaft)revolutions to spin the ring gear/carrier once, and/or the driveshaft/drive pinion gear however many times depending on the gearing ratio. In this case ~4.5 times.

http://home.4x4wire.com/erik/diffs/#ratios

Toyota used 4.56's for rigs that came equipped with 31's from the factory. 4.56's with 33's should still be acceptable. It would probably still be a little low for my liking, but some people like that. Alot of folks will tell you that 4.88's are best for 33's(they're lower not higher than 4.56's BTW). Some will even suggest 5.29's if your running them behind an automatic. Even with the 3.0. I run 35's with 4.30's and happen to think that works perfect with my 3VZE and a manual. It spins ~3000 rpm at 65 MPH, which works out pretty good mileage wise. And when I need power to pass, I drop down a gear and rev it out, or when offroad I'll use 4Low for more torque.

 

4.88s would be best. I have 4.56s and 33x12.5s M/Ts on my '95 4runner 22re 5spd. Its slow, but not too bad. I doubt you will be getting 20+ mpg regardless of gear ratio with 33s. Right now I'm averaging 12.5 mpg city and like 14-15 mixed. And my 22re is in good shape. 5th is useless. 4th is useless under 2700 rpm.
Just because the RPMs are higher, doesnt mean you will be getting worse mpg. In fact, these engines ( at least what I have noticed) get better mpg with a little higher RPM because they dont have to work so hard to stay at speed. When I still ran 31s, my 4runner would get better mpg in 4th gear at 3K rpm than it would in 5th gear at 2600-2700 rpm at hwy speeds. OF course, that was before I redid the exhaust....