What was found
AIRCRAFT WAS GROUNDED: PILOT REPORTS DURING CLIMB OUT PASSING FL190, AIRCRAFT BEGAN PRONOUNCED YAW LEFT TO RIGHT. SHUT OFF RIGHT AUTOPILOT THEN ENGAGED LEFT AUTOPILOT YAW STOPPED THEN STARTED AGAIN SLIGHTLY. SHUT OFF LEFT YAW DAMPER YAW STOPPED. DURING THIS ENTIRE EVENT THERE WERE NO EICAS MESSAGE OR WARNING LIGHTS DISPLAYED. MAINTENANCE ACCOMPLISHED BITE ON THE LT AND RT YAW DAMPERS. LEFT NO FAULTS. RIGHT YAW DAMPER FAULTED. NO HISTORY ON LT AND RT IAW FIM 22-21-00. SUPPLEMENTAL INFORMATION: MAINTENANCE REMOVED AND REPLACED YAW DAMPER P/B PANEL IAW FIM 22-21-00. (CLOSED)