First of all, you have to determine WHERE the slack is coming from. Have someone sit in the seat and work the steering wheel back and forth while you look at all the affected parts in line down from the steering wheel. Joints in steering column, steering box, pitman arm,drag link and joints, tierod and joints. All these parts should move in time with the steering wheel with NO SLOP!! Also check track bar bushings, these have to be TIGHT AND SOLID!!!