Replacing the lower ball joint

            
              The drawings are borrowed from the Citroën CX' parts list

Unscrew the main bolt holding the ball to the arm. Pull aside the metal securing the 2 13mm bolts. Remove the bolts. Knock a screwdriver in between the hub and the ball so you can get a little crack. Replace with larger screwdriver when the gap has got wider (or use a chisel to finish). Put on a puller and tighten. The ball pops out.

Alternative to puller: Place a garage jack on the bolt on the ball bearing and jack up. Hold a sledge hammer against one side of the arm, and knock a couple of times with a heavy hammer on the other side. Will maybe work.