power stear box, 1972 swinger

questiion. when the motor is off there is what i would call too much "play" in the stearing. when the motor is runing there is no play in it. seems normal. is that a mopar thing or am i looking at a box down the road or is it safe. just wondering whats up. the joint seems ok, the play is not there. can the nut be tightened a little on the worm gear to get less play. just looking for experence education. tks Mike