MoonShadow (9/22/2006)
I have a 57 up, red, 19 tooth speedometer gear. With a 380 to 1 rear end I'm seeng a 10mph high reading at 30-40mph. What gear would you guys recommend to bring it in line? ChuckIs the speedometer showing the same 10 mph error in reading at 60 mph or is the error twice as much? If you can time your vehicle between some mile markers and let us know exactly what speed the speedometer is showing along with the minutes and/or seconds between mile markers, then the percent error can be more accurately determined. And with that information, along with knowing that you've got a 19 tooth gear, it might be possible to get you a speedo gear that may correct the error. Doing it this way takes the tire diameter out of the equation. As it stands right now, you'll need a speedo gear with more teeth to slow down the reading. Each tooth increase will slow the speedometer reading down approximately 5% but you'll need some more specific numbers at higher speeds in order to be accurate. And it's possible the gear that slides over the output shaft will also need to be changed depending upon how far off you are.
And as Daniel suggested, your speedometer itself may be the problem.