1978 Corvette Speedometer/Cruise Control Dead

Best guess. The cable used is some of corvettes had plastic ends. To fit into plastic parts. More than likely. The reason for the binding on cable was poor lube from the manufacture. Basical the end of the connection was twisted off. No connection. Lubing will not fix the problem. Also make sure that the cable did not damage the speedo connection. You may find a broken connection from the cable still inside the speedo. But be careful of the printed circuit plastic on the back of the panel. Good luck!