SER.MAN.UPDATE TRANS REPAIRS TRANS. DISASSEMBLY SECTION

Subject: AUTOMATIC TRANSMISSION CHARTS AND ARTWORK UPDATES

Model and Year: 1991 C/K, R/V, P TRUCKS AND G VAN WITH 4L80-E/4L80-EHD AUTOMATIC TRANSMISSION

BULLETIN COVERS:

HYDRA-MATIC 4L80-E/4L80-EHD Transmission updates,occurring after Unit Repair Manual printing.

LIGHT DUTY TRUCK UNIT REPAIR MANUAL:

Add Notice - Transmission Disassembly Section: NOTICE: It is not recommended to use air powered tools to disassemble or assemble transmissions/transaxles. Improper bolt torques can contribute to transmission misdiagnosis and repairs. This information, vital to diagnosis, can only be obtained using hand tools.

Add Caution Notice - Torque Converter: CAUTION: Torque Converter Assembly is in excess of twenty pounds heavier than the 4L60 converter. Use care when removing Torque Converter (1). Personal injury could result.

Add Notice - Pan and Filter Assembly Section: NOTICE: Gasket (29) is reusable.

Change Tool Number - Pump Assembly Section: (Figures 1 & 2) J 38789 Pump Remover should read J 37789 Pump Remover.

Sprag Assembly Section - New Chart for Clutch Plate Application: Direct clutch - corrected piston travel check. (Figure 3)

Forward Clutch Assembly Section: Assembly of the Forward Clutch Piston - Seal Protector Outer Tool J-21409 should read J-38732 Seal Protector Outer. New Chart for Clutch Plate Application: Forward Clutch - corrected piston travel check. (Figure 4)

Pump Assembly Section: Tools Required - J-38789 Pump Installer/Remover should read J-37789 Install or Connect. Use J-37789, not J-38789. (Figure 5)

Control Valve Assembly Section: Install or Connect - Guide Pin Set J-25025-B should read J-25025-5.

Transmission Assembly Section: Gear Unit and Output Assemblies - Inspect #7 Ring Output Speed Sensor illustration number should read 660.

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.