What was found
APPROX 4 MINUTES INTO FLIGHT WITH AUTOPILOT ENGAGED, AP PITCH TRIM MESSAGE CAME ON. CREW FOLLOWED PROCEDURES, BUT MESSAGE RESUMED. THIS OCCURRED SEVERAL TIMES FOLLOWED BY A NOSE DOWN MESSAGE. CREW PERFORMED PRECAUTIONARY STEPS FOR SLIGHT TO MODERATE CONTROLLABILITY PROBLEMS AND DECLARED AN EMERGENCY. CREW RETURNED TO DFW AND LANDED SAFELY. MAINTENANCE REMOVED, CLEANED, AND INSPECTED, AND LUBRICATED THE HORIZONTAL STAB PIVOT POINT OUTER PINS IAW SL RJ-SL-55-001. THE INSPECTINO REVEALED NO DEFECTS. MAINTENANCE CHANGED THE HORIZONTAL STAB TRIM ACTUATOR. OPERATIONAL CHECKS WERE GOOD. AIRCRAFT RETURNED TO SERVICE. (M)