NeilBlanchard wrote:I think that both the speedometer and the odometer are tied together. So, if one is off, then they both are.
In most cars, they are driven by the same speedometer cable, or electronic sensor in newer cars, but that doesn't mean they are off by the same percentage. In a mechanical speedometer, there are 2 separate internal mechanisms that drive the odometer vs the speedometer. So, as in the case of my Mazda 626GT, the cable was driving both instruments 4% too fast, but then the speedometer part of the mechanism was another 3% high on calibration.
On some cars, you can order a speedometer drive gear for the transmission that has a different ratio, and correct the error that way. I seem to remember some of the DSM cars were shipped with the wrong speedo gear, and the fix was to order the right dealer replacement gear. I don't know if Nissan drive gears are interchangeable.