It took me 3 tries to pass algebra in high school a decade and a half ago.
I'm going to swap out gears in my beater s10 while I have the diff apart, and I'm smart enough to not trust my maths.
Stock gears are 3.73
Stock tires are 215/65-r15 (about 26 inches?)
Using http://www.differentials.com/technical-help… it says I should be turning ~2507rpm at 65 mph.
I currently have 31x10.5 tires, and its a bit doggy at low rpms (for obvious reasons)
So the site says I'm actually turning 2102rpm at 65 mph.
4.10 gears will put me at 2311rpm, and 4.56 will put me at 2570rpm.
Now, its almost 1am so I havent stuck a tape measure against the tires, but assuming that everything checks out, I should be looking at 4.56 gears, unless I can find a cheap set of some 4.30's or something odd. (4.30 would put me at 2424rpm, which would be ideal.) I think I got everything figured out, but if somebody could eyeball it and point out any obvious mistakes I would appreciate it.