odo vs speedo
 

I have recently put 315 75 16 tires on my first gen. i checked my new speed with a GPS. its dead on or within a mile an hour or so. but my odometer is off by a ton. i dont know if someone altered the speedo gear prior to my ownership. and i thought the speedo was ran off the odometer gear, which i fixed the odo gear already. any input or thoughts would be great