Hey guy just got engine running after paint etc. Did auto-manual trans swap too. Car still on jackstands.
When I let clutch out in neutral, the speedometer went completely around.
I know did something wrong somewhere upon install, anyone give me a hint?

 

Did you swap over the manual trans speedometer cable? That's the only wildcard as everything else I can think of is interchangeable between the manual and automatic transmission. The only other thing is the speedometer drive gear may be different and one for the manual transmission should have been used. You also have to confirm that the drive gear you are using is compatible with the speedometer in your car. Meaning if your car is a 1981, the later 1983 or 84 or 85 speedometer drive gear would not work as the speedometer calibration is different.

 

Mechanical speedometers are calibrated based on speedometer cable speed. They will register the correct MPH at a specific cable RPM as long as the magnet in the speedometer is magnetized correctly. Below is the cable RPM calibration for indicated speeds in an Asian speedometer.

• 1024 = 60MPH
• 2048 = 120MPH

I don;t think there is any way that you are spinning the speedometer cable this fast even if you are in gear and not in neutral when you release the clutch. Also the amount of error that can be caused by mismatch speedometer gears in the transmission cannot create what you are describing.

I think the speedometer it self is bad. You can prove this my removing the speedometer cable from the trans and spinning the cable by hand counter clockwise. If the needle pegs or jumps allot when you do this, the speedometer portion of the instrument is seized. If you can't spin it by hand, hook the cable to a drill and run it in reverse. Remember, the cable has to spin at 1024 RPMs counter clockwise just to indicate 60MPM.