replaced speedometer driven gear with recommended 40 tooth and still not accurate...

I don't know what happened but now the speedometer reading is right on the money at all speeds and matches the gps reading. The needle no longer bounces at 10mph and under. Smooth and accurate. I have no idea why. Thanks again for the help.

Perhaps when you disturbed the cable and put it back on, it picked up a slight bind which would keep it from turning as it should. I had similar issues when I replaced my speedo cable. The bouncing under 10 was probably the cable binding and release, bind and release. Anywho, glad ya got it.