SMU-SECTION 7A - TRANSMISSION UNIT REPAIR

REVISION: 03/23/94

THIS BULLETIN IS BEING REVISED TO CORRECT A UNIT REPAIR MANUAL PAGE REFERENCE, AND TO ADD A FIGURE THAT WAS OMITTED FROM THE FIRST PUBLICATION.

PLEASE DISCARD CORPORATE BULLETIN #377149. ----------------------------------------------------------------------

SUBJECT: SERVICE MANUAL UPDATE - SECTION 7A - TRANSMISSION DIAGNOSIS AND SECTION 7B - TRANSMISSION UNIT REPAIR

MODELS: 1994 CHEVROLET AND GMC TRUCK, C/K TRUCK, P TRUCK, AND G VAN

TRANSMISSION APPLICATIONS:

1994 HYDRA-MATIC 4L80-E/4L80-EHD (MT1)

SERVICE INFORMATION:

DIAGNOSIS PAGE 7A-17A-21 THROUGH 7A-17A-24, MALFUNCTION CODE DIAGNOSIS AND DEFAULT CHARTS;

SPECIFIC ENGINE DESIGNATORS CHANGED IN CODES 21, 22, AND 74, COLUMN HEADING "PROBABLE CAUSE" CHANGED TO "CODE SETTING CRITERIA", CORRECTIONS MADE TO THE CODE SETTING CRITERIA FOR CODES 39, 53, 58, 73, 75, AND 85; CORRECTIONS MADE TO THE DEFAULT ACTION COLUMN FOR CODES 39, 52, 53, 58, 68, 72, 73, 75, 86 AND 87; THE WORD "INHIBIT" IS CHANGED TO "NO" IN CODES 21, 22, 28, 52, 53, 68, 71, 74, 75, 81 AND 83; "SOFT LANDING" IS DEFINED IN CODE 75; AND, SYMBOLS ARE CHANGED TO WORDS IN CODES 28, 37 AND 38.

PAGE 7A-17A-57, 4L80-E/4L80-EHD WIRING DIAGRAM WIRE COLORS UPDATED AND TRANSMISSION COMPONENT TERMINAL DESIGNATORS CORRECTED.

PAGE 7A-17A-58, 4L80-E/4L80-EHD COMPONENT RESISTANCE CHART WIRE COLORS UPDATED.

PAGE 7A-17-59, 4L80-E TRANSMISSION PRESSURE SWITCH ASSEMBLY RESISTANCE CHECK ADDED "TURN ENGINE OFF", CORRECTED REFERENCE FOR INTERMITTENT CONDITION AND HIGH/LOW RESISTANCE DEFINITION BELOW CHART.

UNIT REPAIR

PAGES 7A-17B-36 AND 7A-17B-37, PUMP ASSEMBLY STEP #3; PRESSURE REGULATOR (231) AND BOOST VALVE ASSEMBLY (228) DESIGNATORS CORRECTED. ILLUSTRATION UPDATED TO SHOW THE VALVE BORE PLUG (232) FOR THE PRESSURE REGULATOR (231) AND THE BOOST VALVE ASSEMBLY (228) CHANGED TO THE SAME PLUG AS THE TCC VALVE (233).

PAGE 7A-17B-38, FIGURE 71, MEASURING PUMP BODY FACE TO GEAR CLEARANCE PUMP DRIVEN GEAR (204) AND PUMP DRIVE GEAR (205) DESIGNATORS CORRECTED ON ILLUSTRATION.

PAGE 7A-17B-39, FIGURE 73, ASSEMBLING PUMP BODY AND PUMP COVER PUMP BODY AND COVER ALIGNMENT BAND TOOL DESIGNATION (J 21368) ADDED TO ILLUSTRATION.

PAGE 7A-17B-52, FIGURE 98, INSTALLING FOURTH CLUTCH SNAP RING AND FIGURE 99, INSTALLING GASKET, PUMP COVER TO CASE CORRECTED ILLUSTRATIONS TO MATCH TITLES.

SERVICE MANUAL REFERENCE: PLEASE INSERT THE FOLLOWING PAGES INTO YOUR 1994 SERVICE MANUAL, 4L80-E AUTOMATIC TRANSMISSION DIAGNOSIS AND 4L80-E AUTOMATIC TRANSMISSION UNIT REPAIR SECTIONS.

FIGURES: 12

GENERAL MOTORS BULLETINS ARE INTENDED FOR USE BY PROFESSIONAL TECHNICIANS, NOT A "DO-IT-YOURSELFER." THEY ARE WRITTEN TO INFORM THOSE TECHNICIANS OF CONDITIONS OCCURRING 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 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.

COPYRIGHT 1994. GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.