Speedo's are typically driven by a gear and cable off the transmission, which I beleive in your case would qualify for the drive wheels. In other words, if you put the car on a dyno (or jack stands) and put it in gear, the car would not actually be moving, but would indicate true road speed. Your high tech new car might have an electronic pickup on the drive line instead of a cable. I have never seen a speedo driven by anything other than the drive train. Hope that helps.

------------------
Deezel
87 300TDT
150,000 miles