Yes, quattro I agree it has to be the speedometer. Thanks for the reply! I recently picked a used speedometer and using a drill to spin it compared the one I bought with the one in the car. The one I bought appears to be more accurate. I will switch it out in a week or two to compare in the car with GPS readings.
Has anyone changed the odometer values? Is it relatively easy without affecting the speedometer inner-workings? If the speedometer that I bought is more accurate, I would like to set the odometer to 00000 to match roughly the same value that's in the car.