What was found
ORD - ON TAKE OFF, AIRCRAFT YAWED TO THE RIGHT. FLIGHT ATTENDANTS REPORTED LOUD PBP BEFORE FLIGHT CREW ABORTED TAKEOFF. BRAKE TEMPERATURES DID NOT EXCEED 150 DEGREES. AIRCRAFT TAKEN OUT OF SERVICE FOR EVALUATION. REPLACED NUMBER THREE AND FOUR MAIN LANDING GEAR TIRES AND NUMBER THREE AND FOUR BRAKES. REPLACED LEFT ENGINE ON 07 DECEMBER 2006 AT ORD DUE TO DISTRESSED COMPRESSOR STATE 12 AND 13 BLADES. SYSTEM GROUND CHECKED NORMAL OPERATION.