Speedometer Cable Help

[notahybrid]

Yo, my speedometer is not working and has not since I got the truck (68 C10). I assumed that it was the missing driven gear so I got the correct one and confirmed that there is a drive gear in the transmission.

I noticed that the cable with the end going in the speedometer is noticeably smaller than the hole it goes into. I would say that the end of the cable that should be turning the gague is about 1/16" wide. Does the hole get smaller inside? As far as I can tell this is the original gague cluster, but I'm not sure about the cable. The gear did slide over the cable on the transmission end. Could there be a problem inside the gague? Do these these cables break often internally?

Thanks