Was able to get my project on the road yesterday and the speedometer was reading 80 when I know traffic was only 60-65. This is a 67 Malibu that had a powerglide which has been switched out with a 350 turbo. I assume that the speedometer was geared different for the 2 and 3 speed autos. I bet this is a simple matter to correct once you have an idea what to do.

Check out the BowTie Overdrives site. They will tell you what to do and even sell you the new gears you'll need.

Was able to get my project on the road yesterday and the speedometer was reading 80 when I know traffic was only 60-65. This is a 67 Malibu that had a powerglide which has been switched out with a 350 turbo. I assume that the speedometer was geared different for the 2 and 3 speed autos. I bet this is a simple matter to correct once you have an idea what to do.


Check out these two sights for information and parts

http://www.novaresource.org/speedo.htm

http://www.transmissioncenter.org/GM_Speedometer_Gears.htm#Speedometer_Cables

Have someone pace you so you know exactly how much faster your speedometer is reading (a faster speed will give a more reliable answer).Take the speedometer cable off at the transmission, remove the driven gear and count the number of teeth. Now it's time for a little math. Divide your actual speed with the speed of your "pace" car. For example: 80/60=1 1/3. Multiply the number of teeth on your driven gear by the answer to find out how many teeth you need on the new gear. If you are lucky, there will be a gear available with that number of teeth. If you aren't lucky, you may need to replace the drive gear with a different one to get the necessary ratio.

I got my driven gear from NPD for about $6.

Tom

This is an awesome site. If you look closely on it you can find the GM part numbers to make ordering easier.

http://www.tciauto.com/Products/TechInfo/speedo_gears.asp