What was found
(CAN) PILOT YOKE BINDING DURING APPROACH. USING PITCH DISCONNECT HANDLE, COPILOT YOKE FELT NORMAL. FORCE FELT LIGHTER AS FLAPS EXTENDED. AUTOPILOT DISCONNECTED TO VERIFY A FLAP INDICATION AT A LOWER ALT & GREATER THAN NORM FORCE REQUIRED TO MOVE YOKE FORWARD. CONTROLS RELAXED TO FEEL CONTROLLABILITY, AN ABRASIVE NOISE HEARD. FORCE REQUIRED TO MOVE CONTROLS WERE LIGHTER THAN NORM. APPROACH COMPLETED. AUTOPILOT SERVO MECHANISM FOR ELEVATOR HAS BEEN REMOVED & REPLACED & A/C RETURNED TO SERVICE. AUTOPILOT SERVO RETURNED TO COLLINS FOR INVEST THAT REVEALED A PIECE OF ADHESIVE STUCK BETWEEN DIAPHRAGM & GEARSHAFT. IT WAS DETERMINED THAT AN EXCESSIVE AMOUNT OF ADHESIVE DURING ASSY PROCESS OF SHAFT CAUSED INCIDENT.