Speedometer is slow and oscillates
 

2004 Santa Fe 75K miles, 3.5L with 5 spd auto, 2wd. Speedometer reads slow and at higher speeds the needle oscillates back and forth over a 5-7 mph range.
At slower speeds (20-30 mph) it is pretty close. When it reads 45 the vehicle is going 60+. Above 50 indicated it starts to oscillate.