SUMMARY:RECENT ROCKWELL DEFECT REPORT IDENTIFIED THE FOLLOWING CONCERNS:A: INSUFFICIENT AIR PRESSURE DUE TO INADEQUATE AIR COMPRESSOR CAPACITY;B: AIR HORN PLUMBED INTO AIR SYSTEM WITHOUT PRESSURE PROTECTION VALVE;C: BRAKE IMBALANCE CAUSED BY BRAKE PROPORTIONING VALVES WHICH REDUCE FRONT AXLE BRAKE LINE PRESSURETHE PROBLEMS IDENTIFIED ABOVE MAY RESULT IN HEAT CHECKING ANDCRACKING OF THE REAR DRUMS.