PRESSURE REGULATOR VALVE BUZZ DIAGNOSIS - THM125

TO DIAGNOSE A "BUZZING NOISE", IN AN X-BODY CAR, WHICH CAN BE DETECTED ONLY AT CURB IDLE ENGINE SPEEDS, USE THE FOLLOWING SERVICE INFORMATION SERVICE INFORMATION: 1.VERIFY THAT THE BUZZING NOISE IS FROM THE TRANSMISSION; NOT FROM THE ENGINE OR ANY OTHER PART OF THE AUTOMOBILE. 2.CHECK FOR ENGINE COOLANT IN THE TRANSMISSION OIL. 3.CHECK AND CORRECT THE TRANSMISSION OIL LEVEL. RECHECK FOR THE BUZZING NOISE. 4.IF THE BUZZ IS NOT CORRECTED, REMOVE THE OIL PAN AND CHECK FOR A PLUGGED OR DAMAGED OIL STRAINER. ALSO, CHECK FOR A MISSING OR DAMAGED OIL STRAINER "O" RING SEAL. REPLACE PARTS IF NECESSARY AND RECHECK FOR BUZZING NOISE. 5.IF THE NOISE IS STILL PRESENT, CHECK THE TRANSMISSION SERIAL NUMBER. IF THE TRANSMISSION WAS BUILT PRIOR TO THE BREAK POINT SERIAL NUMBERS LISTED BELOW, THE BUZZ NOISE MAY BE COMING FROM THE PRESSURE REGULATOR VALVE LOCATED IN THE VALVE BODY. TO CORRECT THE NOISE, REPLACE THE VALVE BODY USING THE FOLLOWING PART NUMBERS. PLEASE USE THE FOLLOWING CHART TO UPDATE HYDRA-MATIC SERVICE BULLETIN HM 81-32: VALVE BODY SERVICE PACKAGE *BREAK POINT SERIAL NUMBERS 80-CV-ALL PART NUMBERS 8637958 *BREAK POINT SERIAL NUMBERS 80-PZ-ALL PART NUMBERS 8637957 *BREAK POINT SERIAL NUMBERS 81-CD-28748 PART NUMBERS 8637961 *BREAK POINT SERIAL NUMBERS 81-CG-2756 PART NUMBERS 8637960 *BREAK POINT SERIAL NUMBERS 81-CT-13403 PART NUMBERS 8637960 *BREAK POINT SERIAL NUMBERS 81-CV-159388 PART NUMBERS 8637960 *BREAK POINT SERIAL NUMBERS 81-PZ-268655 PART NUMBERS 8637959 *BREAK POINT SERIAL NUMBERS 82-CI-1017 PART NUMBERS 8637986 *BREAK POINT SERIAL NUMBERS 82-CJ-1053 PART NUMBERS 8637986 *BREAK POINT SERIAL NUMBERS 82-EA-1009 PART NUMBERS 8637921 *ANY 1982 MODEL NOT SHOWN ON THIS CHART WAS BUILT WITH THE NEW DESIGN VALVE BODY FROM START OF PRODUCTION.

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.