My speedometer has always "jumped" around at random speeds. Mostly highway and neighborhood driving speeds I guess. I attempted to replace the Vehicle Speed Sensor, but unfortunately the OEM replacement doesnt fit. It's like 1 mm off. Another weird thing is that when I know it has the wrong speed displayed, if I tap on the gauge, it jumps back to place. I do have aftermarket white face gauges installed, but this problem began BEFORE i installed them. I have a 96 Mustang V6 by the way.