What was found
IN ALL MODES (TURN KNOB & HEADING SELECT) AIRCRAFT ROLL JERKY. AUTOPILOT WILL NOT TRACK COURSE ON GPS. DISENGAGED NAV/LOC ON AUTOPILOT, AIRCRAFT ROLLED LEFT WITH JERKY MOTION INTO 30DEG. LEFT BANK. THEN TURN KNOB WOULD NOT BANK RIGHT UNTIL AUTOPILOT WAS DISENGAGED/REENGAGED (THIS WAS IN BOTH A&B MODES). DEFERRED AUTOPILOT SYSTEM PER MEL 22-1 PLACARD INSTALLED. T/S SYS, FOUND A/P AILERON SERVO TO BE WEAK AND JERKY. REMOVED AND REPLACED AILERON SERVO AND OPS CHECKED IAW B727 MM 22-11-11.