Front end noise when coasting!!!! HELP

I have a 1978 ford with the dana 44 front end. Just recently it has been making an almost grinding noise when I let off the gas from the front end. When I hit the gas it quits. And when I take it out of gear and coast it just gets worse. I have very little experience with front ends as I usually work on engines. I do not know if it is a ujoint but they all seem tight. Also I can turn the yoke on the differential considerably in each direction, maybe 1/8 of a turn. Is this normal or is my lash off? What shold I do? Any suggestions?