SUMMARY:ATHEY PUBLISHED A SERVICE BULLETIN DESCRIBING A DRUM TO DISCBRAKE CONVERSION.A CHECK OF THE ODI DATA BASE REVEALED A COMPLAINTPERTAINING TO FOUR UNITS WHICH HAD EXPERIENCED SEVERE BRAKE PROBLEMS,SUCH AS BLOWN WHEEL CYLINDERS, PREMATURELY WORN BRAKE SHOES, AND BROKENWHEEL CYLINDER PUSH RODS.THE FLEET OWNER CLAIMS THE PRESCRIBED REPAIRIS SAFETY RELATED.THE PROBLEM WARRANTS FURTHER INVESTIGATION.===