EE was replacing the rear suspension cylinder on a CAT 793 truck. As he was using a sledge hammer to drive the top strut pin from its bore he felt a pain in his right wrist. He did not report the incident at that time. On 9/22/06, as he was loosening/tightening the wear plate retaining bolts on a 24M motor grader, using a 3/4"" impact wrench, he again experienced pain in wrist.