I'm swapping in 3.55's in for my current 2.80's. I have 215-60_60 tires ~.25.2" diameter. I think stock driven is 7 tooth? I'm thinking I'll need a 20 tooth driven. There was a chart but I can't seem to find it now.
I've got a Toplader with 3.55 gears. I believe I have the black drive gear and running the 20 or 21 driven gear. It.a pretty much right on as the speed on the speedometer is the same on the cops radar when they pull me over.
Go for a drive and use your phone to compare your actual speed to your speedo's speed. Then determine the percentage your speedometer is off. Then count the teeth on your speedo gear and add the same percentage of teeth to your gear.