BRAKE NOISE OR SQUEAL UPON STOPPING. GMC Truck GMC MD Bus Chassis (B Model) 1997

SUBJECT: BRAKE NOISE OR SQUEAL UPON STOPPING (INSTALL NEW BRAKE PADS)

MODELS: 1990-98 CHEVROLET AND GMC B6/7 MEDIUM DUTY SCHOOL BUSES WITH BENDIX(R) 2.88 INCH HYDRAULIC DISC BRAKES

CONDITION:

SOME OF THE ABOVE VEHICLES MAY EXHIBIT A BRAKE NOISE OR SQUEAL WHEN STOPPING.

CAUSE:

THIS CONDITION MAY BE CAUSED BY THE BUS DUTY CYCLE. SOME DUTY CYCLES THAT INVOLVE A HIGH NUMBER OF STOPS AND HEAVY BRAKE USAGE MAY BE MORE PRONE TO GLAZE THE BRAKE LININGS. BECAUSE OF THIS, THE BRAKES MAY MAKE A HIGH-PITCHED SQUEAK OR SQUEAL UPON STOPPING. THIS BRAKE NOISE DOES NOT AFFECT NORMAL BRAKE OPERATION.

ALTHOUGH SOME BRAKE NOISE IS CONSIDERED NORMAL, THE COMPOSITION OF THE BRAKE LINING MATERIAL MAY BE A CONTRIBUTING FACTOR. VARIOUS LINING MATERIALS REACT DIFFERENTLY IN HEAVY USAGE DUTY CYCLES, AND MAY BE MORE OR LESS RESISTANT TO BRAKE SQUEAL.

CORRECTION:

A NEW PERFORMANCE FRICTION(TM) LINING MATERIAL HAS BEEN RELEASED FOR THE BENDIX(R) 2.88 INCH CALIPER SCHOOL BUS APPLICATION. INSTALL THIS NEW MATERIAL ON AFFECTED VEHICLES. USE THE P/N LISTED BELOW. REFER TO SECTION 5B OF THE MEDIUM DUTY SERVICE MANUAL.

IMPORTANT: REMEMBER TO LUBRICATE THE CALIPER SLIDE RAILS, THE CALIPER HOUSING, AND THE SUPPORT SPRING WITH GOODWRENCH BRAKE CALIPER LUBRICANT (AEROSHELL #5). THIS LUBRICANT, P/N 12377969, IS AVAILABLE THROUGH GMSPO.

DO THIS LUBRICATION EVERY 29,000 KM (18,000 MI) OR 6 MONTHS, WHICHEVER OCCURS FIRST, AND WHENEVER YOU SERVICE THE BRAKE CALIPERS. REFER TO CORPORATE BULLETIN NUMBER 66-50-13, DATED APRIL 1997, FOR FURTHER INFORMATION.

PARTS INFORMATION:

P/N DESCRIPTION QTY --- ----------- ---

12474463 PAD KIT, FRT. DISC BRAKE 1

PARTS ARE EXPECTED TO BE AVAILABLE 8-24-98 FROM GMSPO.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION LABOR OPERATION NUMBER DESCRIPTION TIME --------------- ----------- ---------------

H0042 FRONT PADS, DISC BRAKE - USE PUBLISHED LABOR R+R OR REPLACE OPERATION TIME

H0043 REAR PADS, DISC BRAKE - USE PUBLISHED LABOR R+R OR REPLACE OPERATION TIME

FIGURES: 00 ATTACHMENTS: 00

GENERAL MOTORS BULLETINS ARE INTENDED FOR USE BY PROFESSIONAL TECHNICIANS, NOT A "DO-IT-YOURSELFER". THEY ARE WRITTEN TO INFORM THOSE TECHNICIANS OF CONDITIONS THAT MAY OCCUR ON SOME VEHICLES, OR TO PROVIDE INFORMATION THAT COULD ASSIST IN THE PROPER SERVICE OF A VEHICLE. PROPERLY TRAINED TECHNICIANS HAVE THE EQUIPMENT, TOOLS, SAFETY INSTRUCTIONS AND KNOW-HOW TO DO A JOB PROPERLY AND SAFELY. IF A CONDITION IS DESCRIBED, DO NOT ASSUME THAT THE BULLETIN APPLIES TO YOUR VEHICLE, OR THAT YOUR VEHICLE WILL HAVE THAT CONDITION. SEE A GENERAL MOTORS DEALER SERVICING YOUR BRAND OF GENERAL MOTORS VEHICLE FOR INFORMATION ON WHETHER YOUR VEHICLE MAY BENEFIT FROM THE INFORMATION.