THE PETERBILT 320 - WITH AN ALLISON 754 HT TRANSMISSION (AUTOMATIC MECHANICAL) HAS TWO (2) SEPARATE DEADLY DEFECTS: ILLUSORY NEUTRAL DEFECT - SHIFT INDICATOR IN CAB READS NEUTRAL AND VIBRATION OF VEHICLE CAUSES THE TRANSMISSION TO GO INTO GEAR. THIS VEHICLE IS USUALLY USED AS REFUSE VEHICLES. THIS DEFECTS OCCURS USUALLY WHEN PTO IS ON, WHICH CAUSES HIGH RPMS. THE DRIVER THINKS THE TRANSMISSION IS IN NEUTRAL BECAUSE THE SHIFT INDICATOR IN THE CAB SHOWS NEUTRAL AND THE TRANSMISSION IS NOT ENGAGED (THAT IS, THE VEHICLE WILL REMAIN MOTIONLESS ON LEVEL GROUND). . INSTEAD, THE TRANSMISSION IS REALLY IS IN BETWEEN THE NEUTRAL AND DRIVE POSITIONS. THE VIBRATION FROM THE PTO CAUSES THE TRANSMISSION TO UNEXPECTEDLY DROP INTO DRIVE. THE ALLISON AUTOMATIC TRANSMISSION DROPS INTO DRIVE (WITH HIGH RPMS) AND THE PARKING BRAKE DOES NOT HOLD VEHICLE. THUS, THE BRAKES ARE DEFECTIVE AND THE TRANSMISSION IS DEFECTIVE. IN ADDITION TO A FATALITY, WE HAVE MANY DRIVERS WHO HAVE EXPERIENCED THIS SAME DEFECT. THE ILLUSORY NEUTRAL DEFECT OCCURS AFTER SHIFT CABLE STRETCHES AND/OR BECOMES MAL-ADJUSTED. *AK