speedometer- need one?

Did you lubricate the cable before putting it in? Dan wrote a nice write up on the slant six board. In summary, without removing the cluster, you reach under the dash and pull the speedo cable out. Put some white lithium grease in between your index and middle fingers. Put both hands under the dash and push the speedo cable through the grease between your fingers and into the speedo. See if it still rattles. If it does, you can either send it off to get rebuilt or find one on ebay.