Speedometer ?

[1986Silverado]

Well got the tranny in today and got it running. Installed a new speedo cable cause the old one was broke and previous owner had disconnected it and filled the gear in the tranny with silicone. Anyway....I removed the silicone, installed the cable and all seemed well until I drove it. The cable makes a clicking noise and is consistent and the needle in the guage kinda bounces back and forth and all the way around. The needle also does the bounce or jump at the same time the click is heard Could this be the speedo gear in the tranny? I think it is rounded out but still catching the cable when the click is heard. I also think it is the gear because when I installed the new cable it fell into place to easy.