Possible fix.

I scoured ebay today and found several speedometer cables for the El Camino. I did a buy it now and will replace the original after paint. I have the original speedometer as I replaced it with the one that came with the new dash. Both act the same. I connected a drill motor to the spare and it worked very smooth. I have checked the original cable and couldn't find anything obviously wrong. Anyway a new one is on the way.