DRIVELINE LAUNCH SHUDDER

SUBJECT: DRIVELINE LAUNCH SHUDDER (INSTALL NEWLY DESIGNED PROPELLER SHAFT)

MODELS: 1992-93 CHEVROLET AND GMC TRUCK S10803 MODELS (PICK-UP, REGULAR CAB, AND LONG BED) 1992-94 CHEVROLET AND GMC TRUCK S10653 MODELS (PICK-UP, EXTENDED CAB, AND SHORT BED) 1992-94 CHEVROLET AND GMC TRUCK T10653 MODELS (PICK-UP, EXTENDED CAB, AND SHORT BED) WITH 4.3L V-6 ENGINES (VINS W, Z - RPOS L35, LB4) AND AUTOMATIC TRANSMISSION

CONDITION:

SOME OWNERS OF PICK UPS WITH 4.3L V-6 ENGINES (RPOS L35, LB4), EQUIPPED WITH A TWO-PIECE REAR PROPELLER SHAFT AND AN AUTOMATIC TRANSMISSION, MAY EXPERIENCE A LAUNCH SHUDDER CONDITION. THIS CONDITION MAY OCCUR FROM 0 TO 25 MPH (0-40 KPH) AND IS MORE NOTICEABLE DURING HARD ACCELERATION WHEN THE VEHICLE IS HEAVILY LOADED, OR WHEN USED AS A TOW VEHICLE.

CAUSE:

THIS CONDITION IS CAUSED BY THE DRIVELINE ANGLE CHANGES OCCURRING DURING ENGINE TORQUE AND VEHICLE PAYLOAD.

CORRECTION:

TO REPAIR THIS CONDITION A NEWLY DESIGNED REAR PROPELLER SHAFT AND PINION FLANGE IS RELEASED FOR SERVICE TO REDUCE DRIVELINE LAUNCH SHUDDER DURING 0-25 MPH (0-40 KPH).

SERVICE PROCEDURE:

REMOVE OR DISCONNECT (FIGURES 1, 2, AND 3): TOOL REQUIRED: J8614-01 COMPANION FLANGE HOLDER 1. PLACE THE VEHICLE ON A HOIST THAT WILL ALLOW FREE ROTATION OF THE REAR WHEELS. 2. REMOVE BOTH REAR TIRE WHEEL AND DRUM ASSEMBLIES. 3. REMOVE AND DISCARD EXISTING TWO PIECE REAR PROPELLER SHAFT ASSEMBLY, RETAINING THE STRAPS AND FASTENERS. 4. MEASURE THE PRE-LOAD ON THE REAR AXLE PINION FLANGE USING AN INCH POUND TORQUE WRENCH, THE AMOUNT OF TORQUE REQUIRED TO TURN THE PINION (FIGURE 1). RECORD THIS MEASUREMENT FOR REASSEMBLE PURPOSES. THIS MEASUREMENT WILL GIVE THE COMBINED PINION BEARING AND SEAL PRE-LOAD. ALSO RECORD THE NUMBER OF EXPOSED THREADS BEYOND THE FLANGE NUT ON THE PINION FLANGE NUT. 5. REMOVE THE PINION FLANGE NUT AND WASHER BY USING TOOL J-8614-01 TO HOLD THE PINION FLANGE USING A SOCKET AND DRIVER. DISCARD EXISTING PINION FLANGE, NUT, WASHER, AND SEAL DEFLECTOR (FIGURE 2). 6. REMOVE THE PINION FLANGE USING TOOL J-8614-01, 02 AND 03 (FIGURE 3) WHILE USING A SUITABLE CONTAINER TO CATCH ANY FLUID THAT MAY DRAIN FROM THE REAR AXLE WHEN REMOVING THE PINION FLANGE. 7. INSPECT THE PINION OIL SEAL FOR ANY SIGNS OF DAMAGE OR CONTAMINATION. IF EITHER CONDITION EXISTS, REPLACE THE PINION OIL SEAL (P/N 26026792).

INSTALL OR CONNECT (FIGURES 1, 2, AND 3):

1. APPLY A SEAL LUBRICANT (GM P/N 1052497) TO THE OUTSIDE OF THE PINION FLANGE. 2. INSTALL THE PINION FLANGE.

NOTICE: DO NOT ATTEMPT TO HAMMER THE PINION FLANGE ONTO THE REAR AXLE PINION STEM AS IT MAY CAUSE DAMAGE TO THE PINION BEARINGS.

3. INSTALL THE WASHER AND FLANGE NUT ON THE PINION STEM SHAFT. TIGHTEN: - HOLD THE COMPANION FLANGE WITH J-8614-01 WHILE TIGHTENING THE FLANGE NUT ON THE PINION STEM. - TIGHTEN THE PINION NUT A LITTLE AT A TIME, ROTATING THE PINION OCCASIONALLY TO ENSURE PROPER BEARING SEATING. ALSO, TAKE FREQUENT PINION BEARING TORQUE PRE-LOAD READINGS UNTIL THE ORIGINAL TORQUE VALUE IS OBTAINED (FIGURE 2).

IMPORTANT: IF THE ORIGINAL PRE-LOAD TORQUE VALUE WAS ( (LESS THAN) 3 LB. IN., THEN RESET TORQUE SPECIFICATIONS TO 3-5 LB. IN.

IMPORTANT: IF THE PINION SEAL AND COLLAPSIBLE SPACER ARE REPLACED, THEN REFER TO THE APPROPRIATE UNIT REPAIR MANUAL OF PINION RE-LOAD SPECIFICATIONS.

4. INSTALL THE "DUAL DOUBLE CARDON" TWO PIECE PROPELLER SHAFT AND ATTACHING BOLTS AND NUTS. 5. APPLY A COATING OF GM P/N 12345382 THREAD LOCK OR LOCTITE(R) #242 OR EQUIVALENT TO THE MOUNTING BOLT THREADS TO FLANGE. TIGHTEN: TIGHTEN BOLTS TO 50 N.M (37 LB FT). 6. INSTALL THE REAR AXLE BRAKE DRUM AND WHEEL ASSEMBLIES. 7. ADD LUBRICANT TO THE REAR AXLE AS NECESSARY.

PARTS INFORMATION:

P/N MODEL YEAR DESCRIPTION QTY 12380420 S10653 1992-94 DUAL DOUBLE CARDON 1 PROP, AND FLANGE KIT 12380421 T10653 1992-94 DUAL DOUBLE CARDON 1 PROP, AND FLANGE KIT 12380422 S10803 1992-93 DUAL DOUBLE CARDON 1 PROP, AND FLANGE KIT

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

WARRANTY INFORMATION

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OP DESCRIPTION LABOR TIME F1280 REAR PROPELLER SHAFT, ASSEMBLY (BETWEEN TRANS + REAR AXLE) USE PUBLISHED LABOR OPERATION F2043 FLANGE, PINION SHAFT REPLACE TIME

FIGURES: 3

CAPTIONS: FIGURE 1 - CHECKING PINION PRELOAD FIGURE 2 - INSTALLING/REMOVING PINION FLANGE NUT FIGURE 3 - INSTALLING/REMOVING PINION FLANGE

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 1995 GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.