ODI HAS CONCLUDED THAT PINS ARE MOST LIKELY TO FRACTURE WHEN THREE ESSENTIAL (ALL THREE APPEAR TO BE NECESSARY) FACTORS CONVERGE: (1) TOW BAR LENGTHS AND GEOMETRIES SIMILAR TO THOSE USED EXTENSIVELY IN CALIFORNIA WHICH CAN IMPOSE LEVERAGED EXCESS-ARTICULATION FORCES ON THE PINTLE HOOK ASSEMBLY AND PIN; (2) TRANSFER DUMP VEHICLES THAT HAVE BEEN OPERATED AT FULL TO EXCESS CRAMP MANEUVERS AS INDICATED BY CONTACT DAMAGE / BRUISING / BRINELLING OF THE BODY OF PIN; (3) PINS MANUFACTURED WITH DIMENSIONAL, GEOMETRIC AND/OR SURFACE CONDITION CHARACTERISTICS THAT INCREASE THE RISK OF CRACK INITIATION.ODI HAS RAISED A NUMBER OF OBSERVATIONS AND ISSUES WHICH ARE SUMMARIZED IN THIS REPORT AND THAT HAVE BEEN REVIEWED WITH PACCAR AND PREMIER.FURTHER INVESTIGATION OF THE IDENTIFIED SUSPECT ISSUES ISUNLIKELY TO PROVIDE A DIFFERENT RESOLUTION.FURTHER USE OF AGENCY RESOURCES DOES NOT APPEAR JUSTIFIED SINCE THE AFFECTED MANUFACTURERS HAVE BEEN APPRISED OF ODI FINDINGS, TAKEN CERTAIN RESPONSIVE ACTIONS AND THE REPORTED INCIDENTS HAVE ABATED.ACCORDINGLY, THIS INVESTIGATION IS CLOSED.THE CLOSING OF THIS INVESTIGATION DOES NOT CONSTITUTE A FINDING BY NHTSA THAT A SAFETY-RELATED DEFECT DOES NOT EXIST.THE AGENCY WILL TAKE FURTHER ACTION IF WARRANTED BY THE CIRCUMSTANCES.SEE CLOSING REPORT FOR FURTHER DETAILS.