speedometer acting up

97 4 door 4x4. figure this one, the speedometer doesn't keep up with the brakes. when I come to a stop the speedometer is still droping. I figure about 3 sec difference. So as soon as I come to a complete stop slowing normal from 45-50 mph the speedometer is at 20 mph and droping. the miliage guage and the water temp and oil guages all weok fine. When I start moving the guage is off about 1-2 seconds. by the time I hit 45 It's fine.
If it's broken how hard is it to fix.

Thanks

if anything its the cable, and thats not hard at all, just tight and time. If its electric it might be the sender on the tranny itself.