What was found
NR 3 ENG N2 REACH 112 PERCENT DURING DEPARTURE. THRUST REVERSE LEVERS IDLE AND N2 WAS 10 PERCENT OR HIGHER THAN OTHER ENGS. NR 3 ENG SHUTDOWN AND RETURNED TO FIELD. DUMPED FUEL AND DECLARED EMERGENCY. ATB, INTERCHANGED ENG NR 2 AND 3 N2 INDS. ENG GRND RUN UP PERFORMED BY FLT CREW. AT IDLE PWR ENG NR 2 N2 IND WAS READING APPROX 1.5 PERCENT HIGHER THAN ENG NR 3 WITH AN INCREASE OF RPM. ENG NR 2 INDICATION DIFFERENCE BECAME GREATER 10 PERCENT TLA DIFFERENCE BECAME GREATER. 10 PERCENT TLA DIFFERENCE APPROX 4 PERCENT BOTH N1 MATCHED INDICATION ENG NR 2 HIGHER ENG NR 3 N2 INDS RETURNED TO POS M306224.