What was found
AIRCRAFT WAS GROUNDED: CABIN ODOR (DIRTY SOCK'S) DISSIPATES ON CLIMB OUT. WHILE ACCOMPLISHING THE INITIAL TROUBLESHOOTING FOR THE CABIN ODOR #1 ENGINE N2 WOULD NOT ROTATE, MAINTENANCE WAS UNABLE TO TURN THE ENGINE BY HAND, FOUND THERE WAS NO OIL IN THE IDG. AFTER REMOVING IDG, ENGINE STILL WOULD NOT ROTATE BY HAND. MAINTENANCE INSPECTED THE CHIP DETECTORS & BORESCOPED ENGINE WITH NO FINDINGS NOTED. DETERMINED THE GEARBOX REQUIRED REPLACEMENT & ENGINE CHANGED PER TASK CARD 26L40071004. MAINTENANCE ACCOMPLISHED CABIN ODOR TROUBLESHOOTING TASK CARD 26L00021001 & NO ODORS WERE NOTED.