My speedo is officially wrong

I say get a cluster from the wrecker's and try that...there are gears inside the gauge cluster if I'm not mistaken...if they're messed up..it could mess up the reading....

 

Your spedometer works by having the cable directly drive the silver wheel (red arrow), the copper bit you see is not attached to the silver wheel it floats inside the silver wheel and is directly attached to the spedometer needle. I do believe it works on a magnetic field, the faster the silver wheel spins the farther it will deflect the copper disk and needle. The silver disc also has some gearing in behind it to run the odometer.


This metal tab has the electronics that generate the speed pulse for the computer. It sits in behind the silver disc.


Another pic of the speed pulse generator.

I would suggest that the easiest test for you is to drive a known distance maybe 10 or 20 miles and see how many miles your odometer says you traveled. If it is pretty accurate then the trans gear and cable are okay.