[dap930]

I hope this not your problem, but there is a disk in the transmission with 8 magnets on it. If one or more of these magnets come loose (hopefully goes to the bottom of the transmission) then the speedometer will not read correctly. The speedometer is looking for 8 pulses per tire revolution. Disconnect the puck sensor wires in the tunnel and check with VOM to see if you get 8 pulses per tire revolution with the back of the car jacked up. If there are less than 8 pulses then the magnet carrier inside the transmission is the problem. It can be accessed by removing the transmission side plate. With fewer than 8 pulses the odometer will still read, but not accurately.