The Stovebolt Site Forums The Shop Area Driveline speedometer reading not acurate

The speedometer reading is not correct. Checked out the actual speed using my Garmen GPS. The speedometer reads slower then the actual speed. While travelling at 50 to 55 MPH the actual speedometer reads 45 to 50 MPH. Seems to about 10 miles MPH off at most speeds. I have a '55 1st series with a stock speedometer and a T5 transmission. Any suggestions?

You might be able to fix that with a simple "driven" gear change. Pull the speedo cable off at the tranny, and remove the plastic gear, count the teeth. Since you need to speed your speedometer up you'll need a gear with 1, or possibly 2 fewer teeth.

These guys can figure it out for you and supply the right gear.

Looks like a great web site. I'm going to give these guys a call. Thanks for the information.

Try www.transmissioncenter.net, they have just about everything you would need to recalibrate a speedo.

In my experience checking the driven distance with the gps is a much more accurate way to read the error, and recalibrate the speedometer. Drive for 100 miles or so by the gps, and check it with the odometer. That will let you know if the error is say 10% or more, or less...

If it is off 10 mph at all speeds, changing the ratio will make the problem more complicated. You are pretty lucky to have a constant offset error. If you find that hard to deal with, why not move the needle ahead to correct it.