What was found
ON A POSITION LEG, DURING CLIMB THROUGH FL390 TO FL400. EXPERIENCED A FROZEN ELEVATOR TRIM. BOTH THE ELECTRICAL & MANUAL TRIM WERE AFFECTED. RAN THE ABNORMAL CHECKLIST & DIVERTED. DURING DESCENT PASSING FL 280, STARTED TO REGAIN SOME MOVEMENT OF THE TRIM WHEEL & MOVEMENT FURTHER FREED UP, AND DESCENDED. AFTER LANDING, THE ELECTRICAL TRIM WAS SLOW & MANUAL MODE WAS DIFFICULT TO MOVE. FOUND BOTH ELEVATOR TRIM ACTUATORS CORRODED AND WORN BUSHINGS & SEALS. BOTH ACTUATORS REPLACED SYS RIGGED & OPS CHECKED OK. PERFORMED SATISFACTORY.