inaccurate speedometer

my speedometer is reading 5-6 mph less than what is actual any thoughts and how to fix i have a 97 ranger 4.0 v6

My 02 was doing that for awhile, and if yours keeps doing it, you may want to look at a good set of Mickey-T's or Super Swampers. ;)

Is this a constant linear difference of 5-6 MPH at all speeds? Are you using an OE tire size? Did you do a measured mile calculation? You know AAA will calibrate your speedometer at no cost.