I recently bought a 1990 4Runner and I've found that most of the time, I am in second in the city and 4th on the highway. I have 31" tires. I also have the stock 4.10 ratio. My question is would swapping to 4.88s cure the problem of needing to be in a lower gear all the time? Is it a big enough jump? I am assuming it will increase my fuel economy as I will be able to use a proper gear.

 

Yes, 4.56 is what would have come from the factory with the 31" tire option on a manual tranny:
- http://www.4crawler.com/4x4/4R_TechI...tml#DiffRatios