correcting speedometer

Hey Guys,
Been ages since I posted last. Just replaced my transmission yesterday, FINALLY. No grinding, hard shifting or other problems. Which brings me to my question. How do I figure the correct speedo gear to correct my speedometer? I have stock 3.909 gears, and BF Goodrich 31x10.50-15's on it now, and in 5th gear at 65 mph on my GPS, the speedo shows 53 mph. I took out the driven gear and it has 22 teeth. I have a table for correcting the speed for 4.63 gears, and it looks like the larger the tire, the fewer teeth. Does anyone have a line on this? I can't be the only one to come across this-I'm just not that special. (Mom was right). Any help would be appreciated.

Try this link
http://moldyrabbit.com/liquid/speedo_gear.html

or this one
http://www.tciauto.com/tc/speedometer-gear-calculator/

Thanks I'll check it out.

The sites you posted are helpful for figuring out gear and tire size changes but I'm looking for the mitsu speedo driven gear tooth number. I have info that they offered a few-26,24,23,22 and 21 tooth gears. By math alone I need about a 19 tooth gear and don't know if they ever had it.

Sounds like you want an adapter? Can you get the tranny codes off the plate on the firewall?

These guys might be able to cut a custom adapter for you.

http://www.speedometershop.com/ratio.html

http://www.tacomaspeedometer.com/index/

I hadn't considered that route but it's sure an option. Thanks for the info!