The speedometer is faulty and has to be replaced. One thing you can try is remove the meter and check if transmission oil has crept up from the cable. Oil contamination can result in the symptoms described as it would not allow the plate behind the meter gear to freewheel and allow the magnet to perform its work correctly.
If there are oil contaminations, you can try cleaning with carb cleaner but be careful in order not to dirty the meter face.
Saturday, November 3rd, 2012 AT 11:31 PM