speedometer problem

[54Caddy]

okay my speedo has always bounced around so i figured it was going bad. No it doesnt move at all. at first just the speedometer wouldnt move but the odometer would, now neither work. I have a new lower speedo cable. My truck has the cruise master unit so when i took the upper cable off the unit and spun the cable the speedo worked fine and mover perfectly with no problems. Could i have a problem with the cruise master unit internally, and does any one know if i where to disconnect the lower cable and try spinning the cable it self would it spin the speedometer gauge, if the cruis master isnt ruined. I am trying to get down to what is wrong. The transmission is new and it has a new gear internally for the speedometer. What do you guys think??