LOSS OF 4TH GEAR, SLIPPING IN 4TH GEAR, BUSY 3-4

SUBJECT: LOSS OF 4TH GEAR, SLIPPING IN 4TH GEAR, BUSY 3-4 SHIFTING OR TCC CYCLING (REPLACE SHIFT SOLENOIDS)

MODELS: 1996-97 CHEVROLET AND GMC C/K, G, P TRUCKS 1996-97 AM GENERAL 1996-97 JAGUAR 1996-97 ISUZU 1996-97 ASTON MARTIN 1997 REUMECH ERMETEK WITH HYDRA-MATIC 4L80E TRANSMISSION (RPO MT1)

CONDITION:

SOME OWNERS MAY COMMENT ABOUT A LOSS OF 4TH GEAR, SLIPPING IN 4TH GEAR, BUSY 3-4 SHIFTING OR TORQUE CONVERTER CLUTCH (TCC) CYCLING AND NO DTC'S ARE SETTING.

CAUSE:

SHIFT SOLENOID LEAKING HYDRAULICALLY.

CORRECTION:

IF NORMAL DIAGNOSIS DOES NOT PROVIDE A CORRECTION, FOLLOW THE SOLENOID TEST PROCEDURE LISTED BELOW. REPLACE THE SHIFT SOLENOID IF IT FAILS THE TEST. ALSO VERIFY THAT THE TRANSMISSION COOLING SYSTEM IS OPERATING PROPERLY.

SERVICE INFORMATION (FIGURE 1) STARTING JUNE 23, 1997 (JULIAN DATE 174) ALL HYDRA-MATIC 4L80-E TRANSMISSIONS ARE BEING BUILT WITH THE NEW SOLENOID ASSEMBLIES. THE NEW SOLENOIDS WILL SERVICE ALL 1991 THROUGH 1997 4L80-E APPLICATIONS.

THE ABOVE LISTED CONDITIONS OCCUR MAINLY ON HIGH DUTY CYCLE APPLICATIONS AND/OR WHEN THE TRANSMISSION IS OPERATED UNDER HIGH TEMPERATURE CONDITIONS.

EACH SOLENOID MAY BE TESTED FOR LEAKING USING THE FOLLOWING TEST: 1. REMOVE THE SOLENOID FROM THE CONTROL VALVE BODY. REFER TO THE SERVICE MANUAL FOR THE PROPER PROCEDURE. 2. CLAMP A PIECE 1/2 INCH I.D. OF RUBBER HOSE OVER THE FLUID INLET END OF THE SOLENOID. 3. CONNECT A WIRE FROM ONE OF THE SOLENOID TERMINALS TO THE NEGATIVE TERMINAL (GROUND) OF A BATTERY. 4. APPLY COMPRESSED AIR TO THE RUBBER HOSE. DO NOT USE AIR PRESSURE IN EXCESS OF 120 PSI. EXCESSIVE PRESSURE WILL NOT ALLOW THE CHECK BALL TO SEAT PROPERLY. 5. CONNECT A WIRE FROM THE OTHER SOLENOID TO THE POSITIVE TERMINAL (12 VOLTS) OF THE BATTERY. 6. OBSERVE THE AIR FLOW THROUGH THE SOLENOID. REPLACE THE SOLENOID IF THERE IS AN AIR LEAK WHEN THE SOLENOID IS ENERGIZED.

SERVICE PARTS INFORMATION NEW PART NUMBER DESCRIPTION ----------------------------------------- 10478140 1-2 + 3-4 SHIFT SOLENOID (BLACK) 10478141 2-3 SHIFT SOLENOID (WHITE)

PARTS ARE CURRENTLY AVAILABLE THROUGH GMSPO.

WARRANTY INFORMATION FOR VEHICLES REPAIRED UNDER WARRANTY, USE: LABOR OPERATION: K6555 1-2 SHIFT SOLENOID K6556 2-3 SHIFT SOLENOID

USE PUBLISHED LABOR OPERATION TIME.

FIGURES: 01 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.

COPYRIGHT 1997. GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.