NHTSA Investigation PE04062

TIE ROD TUBE FAILURE

THIS INVESTIGATION WAS PROMPTED BY COMPLAINTS FROM TWO SEPARATE SCHOOL BUSFLEETS.BOTH FLEETS ALLEGED THAT WHILE MANEUVERING IN A PARKING AREA, THE TIE-ROD TUBE DISCONNECTED FROM ONE OF THE TIE-RODS.DANA, FREIGHTLINER AND THOMAS BUILT BUSES RECENTLY COMPLETED EXTENSIVE TESING AND DETERMINED THAT A CRACK MAY INITIATE ON THE INTERNAL THREAD ROOT OF THE TIE ROD.THIS CONDITION IS DUE TO INADEQUATE DAMPENING IN THE CHASSIS SYSTEM TO ACCOUNT FOR NORMAL BRAKE-INDUCED VIBRATION.THESE CRACKS MAY LEAD TO SEPARATION OF THE TIE ROD FROM THE ASSEMBLY.APPROXIMATELY 5,839 DANA STEER AXLES EQUIPPED WITH A CERTAIN TRW TIE ROD ASSEMBLY UTILIZING A CUT THREAD DESIGN ARE INVOLVED:A.1320 AXLE APPLICATIONS, THOMAS PART NUMBER 61110702 AND 61110705 INSTALLED ON THOMAS BUSES WITH 6" BRAKES AND 30" AIR CHAMBERS;B.1460 AXLE APPLICATIONS, THOMAS BUS PART NUMBER 61110707 AND 61110708 INSTALLED WITH 6" BRAKES AND 30" AIR CHAMBERS. THOMAS BUILT BUS WILL REPLACE THE EXISTING TIE ROD ASSEMBLIES WHICH CONTAIN THE CUT THREAD DESIGN WITH A NEW TIE ROD ASSEMBLY THAT UTILIZES A ROLLED THREAD DESIGN.A ROLLED THREAD PROVIDES LESS STRESS ON THE CRITICAL AREA OF THE TIE ROD. A COPY OF THE DEFECT REPORT IS ATTACHED. THIS ACTION RESOLVES THE ISSUES RAISED BY THIS INVESTIGATION.ACCORDINGLY,THIS INVESTIGATION IS CLOSED.

An investigation is a separate record from a recall and from a manufacturer communication. A manufacturer campaign to repair a safety defect or a failure to meet a federal safety standard.