Speedometer ?

I have been in the process of fixing things in my dash in my 66 cuda so i have had the dash out quite a bit. One of the times i had the dash in i had a bad clicking noise and the speedometer was jumpy and eventually pegged. I went ahead and unhooked the cable from the dash after that. When i had the dash out this last time i hooked the cable back up. I dont have a noise anymore after that but no speedo. I thought hmmm. I was up under the car today and found the cable was unhooked at the transmission. I attached it back to the automatic tranny and i still have no noise but no speedo either. Bad speedo? bad cable? needs adjusting? thanks