1977 Mack DM problems

Defect

IN THE EVENT OF TURBOCHARGER COMPRESSOR WHEEL FAILURE, ONE OR MORE OF THE FOUR CAPSCREWS THAT HOLD THE TURBOCHARGER TOGETHER MAY BE STRUCK BY PARTS OF THE COMPRESSOR WHEEL, RESULTING IN THE CAPSCREWS BEING DAMAGED. IF THESE CAPSCREWS ARE DAMAGED TO THE POINT THAT THEY ALLOW THE COMPRESSOR BACK PLATE TO DISLOCATE FROM THE TURBOCHARGER BEARING HOUSING, ENGINE LUBRICATING OIL MAY BE ALLOWED TO ESCAPE UNDER PRESSURE, CONTACTING THE ENGINE EXHAUST MANIFOLD SECTIONS OR TURBOCHARGER TURBINE HOUSING.

Remedy

DEALER WILL INSTALL A SHIELD FOR THE HEADS OF THE FOUR CAPSCREWS, ALONG WITH STRONGER SAE 8 GRADE 8 CAPSCREWS, IF NECESSARY, AT NO COST TO OWNER.

Defect

IN THE INVOLVED TRUCKS IT IS POSSIBLE THE ADJUSTABLE STEERING COLUMN REAR MOUNTING BRACKET COULD FAIL, ALLOWING STEERING WHEEL ASSEMBLY TO FALL DOWN ONTO THE OPERATOR"S LAP.

Remedy

DEALER WILL INSTALL AN ADDITIONAL BRACKET IN THIS AREA TO PREVENT THE STEERING WHEEL FROM DISLOCATING IN THE EVENT OF A BRACKET FAILURE.

Defect

AN IMPROPER PINCH BOLT AND NUT MAY HAVE BEEN USED IN THE CLAMPING OF THE STEERING SHAFT TO THE STEERING GEAR INPUT SHAFT. DUE TO CLAMPING FORCE LOADS APPLIED AT THE BOLT, THE NUT COULD YIELD, RESULTING IN LOOSENESS OF THE INPUT SHAFT YOKE. SHOULD THIS CONDITION GO UNNOTICED, SPLINE WEAR COULD CAUSE SHAFT SEPARATION.

Remedy

VEHICLES WILL BE INSPECTED AND, IF NECESSARY, THE CORRECT FASTENERS WILL BE INSTALLED AT NO CHARGE TO OWNER.

Defect

A CASTING DEFICIENCY EXISTS IN THE LOWER SECTION OF THE CAPS RESULTING IN A REDUCTION IN THE THICKNESS OF THE MATERIAL. FAILURE OF A CAP CAN ALLOW THE END OF THE REAR SPRING TO DETACH FROM THE AXLE HOUSING.

Remedy

DEALER WILL INSPECT AND, IF NECESSARY, REPLACE ANY OF THE SPRING INSULATOR CAPS FOUND TO BE DEFECTIVE. THIS WILL BE DONE AT NO COST TO OWNER.

Defect

DELAYS OF UP TO ABOUT 2 SECONDS MAY EXIST IN THE BRAKE APPLICATION TIMES TO THE BRAKES ON THE BOGIE AXLES IN THE PRESENCE OF CERTAIN TYPES OF WHEEL SPEED SENSOR SIGNAL DISCONTINUITIES OR DISTORTIONS THAT MAY OCCUR AS A RESULT OF SENSOR WIRE FAILURE. THIS CONSTITUTES A NON-COMPLIANCE TO FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 121, "AIR BRAKE SYSTEMS".

Remedy

DEALER WILL INSTALL NEW WHEEL SPEED SENSORS THAT INCORPORATE IMPROVED WIRING AND THE PRESENT BOGIE ANTI-WHEEL LOCK SYSTEM WILL BE CHANGED TO AN AXLE-TO-AXLE SYSTEM FOR IMPROVED RELIABILITY.

Defect

THE EXISTING CROSS STEERING ARMS MAY HAVE INSUFFICIENT FATIGUE LIFE IN THE NECK AREA. THIS IS NEAR THE BOSS FOR THE CROSS STEERING TUBE BALL JOINT CONNECTION. FAILURE OF EITHER OF THE CROSS STEERING LEVERS COULD LEAD TO LOSS OF STEERING CONTROL OF THE RIGHT FRONT WHEEL.

Remedy

THE DEALER WILL INSPECT AND, IF NECESSARY, INSTALL CROSS STEERING ARMS OF IMPROVED DESIGN AND GREATER STRENGTH.

Defect

THE SYNFLEX-TYPE OIL PRESSURE SIGNAL LINE MAY HAVE BEEN ROUTED TOO CLOSE TO THE EXHAUST MANIFOLD. EXCESSIVE HEAT MAY CAUSE THE LINE TO RUPTURE, AND OIL LEAKAGE MAY OCCUR.

Remedy

THE DEALER WILL REROUTE THE OIL PRESSURE SIGNAL LINE TO ELIMINATE POTENTIAL FIRE HAZARD, WITHOUT CHARGE TO OWNER.

Defect

A DEFICIENCY EXISTS IN THE WELDS SECURING THE REAR SPRING INSULATOR BRACKET TO THE AXLE HOUSING. THIS IS DUE TO IMPROPER POSITIONING OF THE WELD, IN RELATIONSHIP TO THE BRACKET AND AXLE HOUSING. FAILURE OF THE WELDS WOULD CAUSE SEPARATION OF THE SPRING INSULATOR BRACKET AND THE AXLE HOUSING, RESULTING IN IMPROPER ALIGNMENT OF THE AFFECTED AXLE.

Remedy

DEALER WILL REWELD THE INSULATOR SPRING BRACKET AT NO COST TO OWNER.

Defect

THE INVOLVED VEHICLES DO NOT CONFORM TO FEDERAL MOTOR VEHICLE SAFETY STANDARD NO. 209, "SEATBELT ASSEMBLIES". ALTHOUGH THE SEATBELTS IN QUESTION PERFORMED MARGINALLY WITH RESPECT TO THE 5000 LB. LOAD REQUIREMENT, ADDITIONAL TESTING CONFIRMED THAT THE ANCHOR COULD FAIL, ALLOWING EITHER THE ANCHOR TO SLIP OVER THE HOLD-DOWN NUT OR THE ANCHOR TO SEPARATE INTO TWO PIECES.

Remedy

DEALER WILL INSPECT AND, IF NECESSARY, REPLACE SEAT BELT ASSEMBLIES WITHOUT CHARGE TO OWNER.

Defect

THE FLEX BLADE FANS ON THE INVOLVED VEHICLES MAY DEVELOP CRACKS IN THE LAMINATED STIFFENER AS A RESULT OF FATIGUE DURING OPERATION. IF SUCH A CONDITION EXISTS AND THE CRACKS GO UNDETECTED, CONTINUED OPERATION COULD CAUSE PIECES OF THE STIFFENER TO BREAK OFF.

Remedy

DEALER WILL REPLACE THE ORIGINAL FAN WITH A STEEL FIXED BLADE FAN, FREE OF CHARGE.

Defect

THE FRONT WHEEL RIM CLAMP STUDS, INSTALLED ON THE INVOLVED VEHICLES, MAY NOT HAVE BEEN MANUFACTURED CORRECTLY, CAUSING A BRITTLE CONDITION IN THE THREAD ROOT AREA. THE STUDS COULD EVENTUALLY CRACK AND BREAK WHEN WHEEL NUTS ARE TIGHTENED TO SPECIFICATIONS.

Remedy

THE DEALER WILL REPLACE ALL SUSPECT FRONT WHEEL STUDS, WITHOUT CHARGE TO OWNER.