Staff Sgt. Charles Pierce replaces a differential. U.S. Air Force Staff Sgt. Charles Pierce replaces a differential on a high mobility wheeled vehicle at Sather Air Base, Iraq, on May 12, 2008. Pierce is deployed from Cannon Air Force Base, N.M. SHARE: Download: Full Size (0.06 MB) Credit: VIRIN: 016746-A-FJR18-994.jpg Photo Gallery