EXPERTEC TSB (267205)

Publication date: 1992-12-03
Reference number: 267205

EXPERTEC TSB

TECHNICAL SERVICE BULLETIN

Reference Number(s): 267205, Date of Issue: 12/03/92

NEUTRAL GEAR RATTLE (REPLACE - PROM AND PILOT BUSHING)

Date: 12/03/1992

Bulletin No.: Oldsmobile 26-72-05

SOME OWNERS OF 1990-92 C/K AND 1990-91 S/T TRUCKS WITH 4.3L ENGINES (RPO LB4) AND 5-SPEED MANUAL TRANSMISSION (RPO'S MG5, MY2) MAY COMMENT THAT THE TRANSMISSION RATTLES WHEN IN NEUTRAL WITH THEIR FOOT OFF THE CLUTCH PEDAL AND THE ENGINE AT IDLE. THE CUSTOMER MAY DESCRIBE THE RATTLE AS LOOSE BEARINGS.

THIS RATTLE NOISE IS CREATED WHEN THE TURNING TRANSMISSION GEARS CONTACT AGAINST EACH OTHER. THE CONTACT IS CREATED BY THE FIRING IMPULSES OF THE ENGINE WHICH CAUSES RAPID ACCELERATION AND DECELERATION OF THE INDIVIDUAL GEARS.

THIS CONDITION MAY BE CORRECTED BY THE INSTALLATION OF THE FOLLOWING PARTS:

- A REVISED CLUTCH DRIVEN DISC WHICH FEATURES A FIVE DEGREE NEUTRAL STAGE. THIS NEUTRAL STAGE HELPS TO SMOOTH THE RAPID ACCELERATION AND DECELERATION OF THE INDIVIDUAL TRANSMISSION GEARS.

- A REVISED PROM WHICH RAISES ENGINE IDLE SPEED TO 650 RPM ON C/K AND 700 RPM ON S/T. THIS INCREASE IN IDLE SPEED HELPS TO SMOOTH THE

ENGINE FIRING PULSES.

- A CLUTCH PILOT BEARING RATHER THAN A CLUTCH PILOT BUSHING. THIS BEARING HELPS TO ISOLATE THE TRANSMISSION FROM THE ENGINE IDLE ACCELERATION / DECELERATION.

SERVICE PROCEDURE:

NOTE: INCORRECT ENGINE IDLE CAN CONTRIBUTE TO NEUTRAL GEAR RATTLE. BEFORE INSTALLING THE PARTS LISTED IN THIS BULLETIN, REFER TO THE APPROPRIATE YEAR LIGHT DUTY TRUCK FUEL AND EMISSIONS SERVICE MANUAL, SECTION 2, DRIVEABILITY SYMPTOMS "ROUGH, UNSTABLE OR INCORRECT IDLE STALLING" TO VERIFY THERE ARE NO EXISTING CONDITIONS CONTRIBUTING TO A ROUGH IDLE WHICH MAY AGGRAVATE NEUTRAL GEAR RATTLE.

CLUTCH DISC AND PILOT BEARING REPLACEMENT: REFER TO THE APPROPRIATE YEAR AND MODEL SERVICE MANUAL, SECTION 7C "CLUTCH ASSEMBLY AND PILOT BEARING REPLACEMENT."

NOTE: C/K TRUCKS REQUIRE PRESSURE PLATE P/N 15668537 WHICH WAS FIRST USED IN PRODUCTION MID-1991. 1990 AND 1991 VEHICLES BUILT PRIOR TO THE FOLLOWING VIN BREAKPOINTS REQUIRE INSTALLATION OF P/N 15668537 UNLESS IT HAS ALREADY BEEN INSTALLED IN A SERVICE REPAIR:

SERVICE INFORMATION

DESCRIPTION	GMC	CHEVROLET
FT. WAYNE (Z)	MZ516555	MZ159936
OSHAWA (1)	M1526826	M1178933
PONTIAC (E)	ME516465	ME152577

PROM REPLACEMENT: REFER TO THE APPROPRIATE YEAR LIGHT DUTY TRUCK FUEL AND EMISSIONS SERVICE MANUAL, SECTION 3 "ON-VEHICLE SERVICE, PROM".

SERVICE PARTS INFORMATION

MODEL	DESCRIPTION	PART NUMBER
1990-92 C/K, 4.3L, 5SP	PLATE, CLUTCH DRIVEN	15961141 *
1990-91 S/T, 4.3L, 5SP	PLATE, CLUTCH DRIVEN	15960226
1990-92 C/K, S/T, 4.3L	BEARING, CLUTCH PILOT	14061685
THIS CLUTCH DISC CAN ONLY BE USED WITH PRESSURE PLATE P/N 15668537. SEE SERVICE PROCEDURE INFORMATION ABOVE FOR MORE DETAILS.

SERVICE INFORMATION

YEAR	MODEL	ENG	TRANS	EMISSION TYPE	SERVICE PROM	B/CAST CODE	SCANNER I.D.
1992 1992 1992 1992 1991 1991 1990 1990	C1,2 K1,2 C1,2 K1,2 CK1,2CK1,2CK1,2CK1,2	LB4LB4LB4LB4LB4LB4LB4LB4	MG5 MG5 MG5 MG5 MG5 MG5 MG5 MG5	FED(NA5)/ALT(NA6)FED(NA5)/ALT(NA6) CAL(NB2) CAL(NB2) FED(NA5)/ALT(NA6) CAL(NB2) FED(NA5)/ALT(NA6) CAL(NB2)	16185334 16184269 16185336 16184270 16184264 16184267 16184264* 16184267*	BDCW BCZP BDCX BCZR BCZK BCZM BCZK BCZM	5565 4445 5575 4455 4405 4425 4405 4425
* THESE PROMS CANONLY BE USED WITH SERVICE ECM P/N 16144288.

SERVICE B/CAST SCANNER

YEAR	MODEL	ENG	TRANS	AXLE	PROM	CODE	I.D.
1990-911990-911990-91	S S/T S/T	LB4LB4LB4	MY2 MY2 MY2	2.73(GU2)3.08(GU4)3.42(GU6)	16184103* 16184104* 16184106*	BCWS BCWT BCWU	4201 4211 4221
* THESE PROMS CAN ONLY BE USED WITH SERVICE ECM P/N 16144288.

PARTS ARE EXPECTED TO BE AVAILABLE ON DECEMBER 14, 1992. IN CASE OF LIMITED INVENTORY, PARTS WILL BE PLACED ON 400 CONTROL TO WAIVE VIP SURCHARGES. ONLY VERIFIABLE EMERGENCY VIP ORDERS WILL BE ACCEPTED. GMSPO WILL MAKE EVERY EFFORT TO OBTAIN PARTS. HOWEVER, THE PART WILL BE SHIPPED PREMIUM TRANSPORTATION AT DEALER'S EXPENSE AND ALL OTHER ORDER TYPES WILL BE PLACED ON BACK ORDER UNTIL THE 400 CONTROL IS REMOVED.

WARRANTY INFORMATION

FOR VEHICLES REPAIRED UNDER WARRANTY USE:

WARRANTY INFORMATION

LABOR OPERATION	LABOR TIME C	LABOR TIME K	LABOR TIME S	LABOR TIME T
T0500 - PROM REPLACE	.6	.6	.6	.6
K0800 - CLUTCH DISC AND PILOT BEARING REPLACE	2.3	3.1	3.0	4.1
ADD: W/SKID PLATE	.2		.2

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.