INFO. ON 1999 GEN 1E SMALL BLOCK V6/V8 NEW PRODUCT. Chevrolet Astro

SUBJECT: INFORMATION ON 1999 GEN 1E SMALL BLOCK V6/V8 NEW PRODUCT SERVICE

MODELS: 1998-99 CHEVROLET AND GMC S/T, M/L, C/K, G AND P MODELS 1998-99 OLDSMOBILE BRAVADA WITH 4.3L, 5.0L OR 5.7L ENGINE (VINS X, W, M, R - RPOS LF6, L35, L30, L31)

THIS BULLETIN ADDRESSES PRODUCT ENHANCEMENTS MADE TO SMALL-BLOCK V6 AND V8 (GEN 1E) ENGINES USED IN THE 1999 TRUCK PRODUCT LINE. ALTHOUGH THESE CHANGES ARE FEW AND MAY SEEM RELATIVELY MINOR, THEY COULD MANIFEST INTO CONSIDERABLE SERVICE CONCERNS TO UNINFORMED SERVICE TECHNICIANS. PLEASE READ CAREFULLY.

NEW FEATURES...1999 MY 4.3L V6, 5.0L AND 5.7L V8

1) ALL ENGINE OIL PRESSURE SWITCH NOW HAS A 1-PIN CONNECTOR. THIS WAS A MID-1998 MODEL YEAR (MY) RUNNING CHANGE THAT ELIMINATED THE REDUNDANT FUEL PUMP POWER CIRCUIT. SEE THE "SERVICE INFORMATION" CHART, BELOW, FOR SPECIFIC SERVICE INFORMATION FOR EACH PLATFORM.

2) 4.3L V6 (VINS X, W - RPOS LF6, L35)

NOTICE: CARE MUST BE TAKEN TO NOT CROSS-THREAD THESE LOCATIONS. THESE LOCATIONS ON THE ENGINE BLOCK ARE NON-SERVICEABLE. ANY DAMAGE DONE TO THREADS IN THESE LOCATIONS WILL REQUIRE A SERVICE ENGINE BLOCK.

METRIC FASTENERS STARTING IN 1999. THE 4.3L ENGINE BLOCK AND OIL PAN WILL BE MACHINED WITH METRIC THREADS AT THE FOLLOWING LOCATIONS.

A) L.H. MOTOR MOUNT BOSS (M10 X 1.5), 3 LOCATIONS B) R.H. MOTOR MOUNT BOSS (M10 X 1.5), 3 LOCATIONS C) STARTER MOUNTING PAD (M10 X 1.5), 2 LOCATIONS D) TRANSMISSION MOUNTING FLANGE, REAR ENGINE BLOCK (M10 X 1.5), 6 LOCATIONS E) TRANSMISSION MOUNTING FLANGE, OIL PAN (M10 X 1.5), 3 OR 4 LOCATIONS

CRANKSHAFT, FLYWHEEL MOUNTING FLANGE CHANGE. STARTING IN 1999, THE CRANKSHAFT WILL HAVE 3.0 MM (APPROX. 1/8 INCH) OF LESS MATERIAL AT THE FLYWHEEL MOUNTING FLANGE. REFERRED TO AS "SHORT CRANK", THE OVERALL LENGTH OF THE CRANKSHAFT HAS NOT CHANGED, BUT THE FLYWHEEL WILL NOW MOUNT 3MM CLOSER TO THE REAR OF THE ENGINE BLOCK. THIS CHANGE REQUIRED OTHER SPECIFIC CHANGES LISTED BELOW.

A) REVISED CRANKSHAFT REAR OIL SEAL HOUSING B) REVISED CRANKSHAFT REAR OIL SEAL C) REVISED CRANKSHAFT REAR OIL SEAL HOUSING STUD LOCATION D) APPLICATION-SPECIFIC FLYWHEELS

KENT-MOORE TOOL J-35621-UPD2 (REAR MAIN SEAL INSTALLER UPDATE KIT) IS REQUIRED TO UPDATE KENT-MOORE TOOL J-35621-A (REAR MAIN SEAL INSTALLER) FOR USE ON THE 1999 4.3L V6. WITH THE ADDITION OF THIS KIT, THE J-35621-B WILL SERVICE BOTH 1999 4.3L V6, AND 1999 (AND PREVIOUS) 5.0L V8/ 5.7L V8/1998 (AND PREVIOUS) 4.3L V6.

THIS CHANGE TO THE CRANKSHAFT WAS MADE TO ADDRESS A REQUIREMENT FOR A "THICKER" TORQUE CONVERTER ON GMT 800 APPLICATIONS. OTHER 4.3L V6 APPLICATIONS WILL HAVE AN OFFSET STAMPED INTO THE FLEX- PLATE, OR MATERIAL ADDED TO THE FLYWHEEL, TO RETAIN PROPER ALIGNMENT OF COMPONENTS. THEREFORE, THESE COMPONENTS SHOULD NOT BE INTERCHANGED.

CRANKSHAFT, MANUAL TRANSMISSION PILOT BEARING. THE 4.3L V6 WILL UTILIZE A NEW BALL BEARING TYPE PILOT BEARING FOR MANUAL TRANSMISSION APPLICATIONS. A NEW KENT-MOORE TOOL J-43276 IS REQUIRED TO REMOVE THIS NEW 4.3L V6 BEARING. THE V8'S WILL RETAIN THE CURRENT (1998) TYPE NEEDLE BEARING.

PRODUCT AVAILABILITY:

DUE TO MARKETING CONCERNS, SOME MODELS MAY HAVE VIN BADGES TO INDICATE ONE MODEL YEAR, BUT THE ENGINE CONTENT MAY ACTUALLY BE OF A PREVIOUS, OR OF A FUTURE YEAR. THIS CAN CAUSE CONFUSION WHEN TRYING TO REFERENCE A MODEL YEAR (MY) FOR SERVICE CONCERNS. TO ADDRESS THIS, TWO RPOS HAVE BEEN DESIGNATED TO INDICATE A MY "PULL AHEAD" OR "PUSH BACK". THESE RPOS (AND AN EXPLANATION) ARE AS FOLLOWS.

1) RPO "ZN4" WHICH MEANS A VEHICLE IS BADGED FOR ONE MODEL YEAR WHILE IT IS BEING MANUFACTURED INTO THE NEXT (PUSHED BACK). A SPECIFIC CASE OF THIS ARE SOME 1998 S/T PICKUP TRUCKS WHICH ARE VIN'D AS 1998, BUT ARE MANUFACTURED AFTER THE TRADITIONAL AUGUST CHANGEOVER, AND CONTAIN 1999 POWERTRAIN COMPONENTS. THESE TRUCKS WOULD CONTAIN RPO "+ZN4".

2) RPO "ZK3" THIS RPO INDICATED A VEHICLE WITH AN INDICATED VIN MY THAT IS "PULLED AHEAD". A SPECIFIC CASE WOULD BE THE GMT 600 VAN WHICH "STARTED" 1999 MY PRODUCTION IN MAY 1998, BUT INCLUDED RPO "+ZK3", WHICH INDICATED 1998 MY CONTENT. WHEN THE CONTENT SWITCHES TO 1999 MY, THE GMT 600 WILL INCLUDE RPO "-ZK3", DESIGNATING 1999 MY CONTENT.

SERVICE INFORMATION:

MY + PLATFORM RPO ENGINE SERVICE INFORMATION

C/K UTILITY, 1999 ALL V8 USE 1998 SERVICE INFORMATION. SUBURBAN +ZK3 (4.3L V6-N/A) USE 3-PIN OIL PRESSURE SWITCH (GMT 400) (P/N 12553175) FOR SERVICE.

1999 ALL V8 USE 1999 SERVICE INFORMATION. -ZK3 (4.3L V6-N/A) USE 1-PIN OIL PRESSURE SWITCH (P/N 10240133) FOR SERVICE.

C/K PICKUP 1999 4.3L V6 USE 1999 SERVICE INFORMATION (GMT 800) USE 1-PIN OIL PRESSURE SWITCH (P/N 10240133) FOR SERVICE. 4.3L V6....METRIC FASTENERS, "SHORT" CRANKSHAFT AND RELATED PARTS.

G VAN 1999 ALL USE 1998 SERVICE INFORMATION. (GMT 600) +ZK3 USE 3-PIN OIL PRESSURE SWITCH (P/N 12553175) FOR SERVICE.

1999 ALL USE 1999 SERVICE INFORMATION. -ZK3 USE 1-PIN OIL PRESSURE SWITCH (P/N 10240133) FOR SERVICE. 4.3L V6....METRIC FASTENERS, "SHORT" CRANKSHAFT AND RELATED PARTS.

S/T PICKUP 1998 4.3L V6 USE 1998 SERVICE INFORMATION. -ZN4 USE 3-PIN OIL PRESSURE SWITCH (P/N 12553175) FOR SERVICE.

S/T PICKUP 1998 4.3L V6 USE 1999 SERVICE INFORMATION. +ZN4 USE 1-PIN OIL PRESSURE SWITCH (P/N 10240133) FOR SERVICE. 4.3L V6....METRIC FASTENERS "SHORT" CRANKSHAFT AND RELATED PARTS.

S/T PICKUP 1999 4.3L V6 USE 1999 SERVICE INFORMATION. USE 1-PIN OIL PRESSURE SWITCH (P/N 10240133) FOR SERVICE. 4.3L V6....METRIC FASTENERS, "SHORT" CRANKSHAFT AND RELATED PARTS.

S/T UTILITY 1999 4.3L V6 USE 1999 SERVICE INFORMATION. USE 1-PIN OIL PRESSURE SWITCH (P/N 10240133) FOR SERVICE. 4.3L V6....METRIC FASTENERS, "SHORT" CRANKSHAFT AND RELATED PARTS.

M/L 1999 4.3L V6 USE 1999 SERVICE INFORMATION. USE 1-PIN OIL PRESSURE SWITCH (P/N 10240133) FOR SERVICE. 4.3L V6....METRIC FASTENERS, "SHORT" CRANKSHAFT AND RELATED PARTS.

P 32/42 1999 ALL USE 1999 SERVICE INFORMATION. USE 1-PIN OIL PRESSURE SWITCH (P/N 10240133) FOR SERVICE. 4.3L V6.... METRIC FASTENERS, "SHORT" CRANKSHAFT AND RELATED PARTS.

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

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.