CV knock off and on

85 West auto trans. On a hundred mile round trip had what I think is a CV knocking on right side . Started as a small tapping and then morphed into a loud hammering. This was happening while moving down the road and not just while turning. It was speed related under acceleration and stopped when I let up. I drove home with the knocking constant. After ordering a new axle from Bus Depot I took the Westy for a drive to confirm knock before installing and on a 20 mile round trip NO knocking from back there so held off installing. I've had a CV go bad before and knock was there all the time only when turning. May take it on a longer run but worried about damage to trans. Anyone have experience with on/off cv noise like this.Spencer