Troubleshoot non working speedometer 81 corvette?

Answer 1

Well... My way requires A trusted friend. First! if you have cruise control there is A transducer under your hood. If not instructions will follow shortly. There will be two speedo cables attached to the t-ducer. I unscrew the speedo cable going from the t-ducer to the cabin and give the square cable tip a thumb finger snap spin in both directions and my trusted friend will either say yeah 30-40-50 mph! or no, nothing. If nothing you need to disconnect the cable from the back of the speedo gauge inside and pinch this square cable tip while the same trusted friend spins the other end proving the cable is good. If the speedo jumps then unscrew the other cable going from the t-ducer to the trans and try to spin the square tip of this cable. this one SHOULD NOT TURN FOR IT IS DIRECTLY CONNECTED TO YOUR FINAL DRIVE GEAR on the back of your trans and should be stiff. If this one spins the cable has come un threaded from the back of your trans or has broke. Finally if you have no cruise control dump that thing and get A Vette with some options! just kidding. You got to unscrew the speedo cable from under the back of the trans and give it the same snap spin in both directions with A trusted friend Watching the speedo NOT SITTING IN THE JACKED UP CAR WITH YOU UNDERNEATH! and the same friend will either say yes it jumped on no nothing. Then follow the steps above. Hope this helps