SHIFT LEVER STUCK IN, OR BLOCKED OUT OF OVERDRIVE

SUBJECT: SHIFT LEVER STUCK IN OR BLOCKED OUT OF OVERDRIVE OR REVERSE (INSTALL REVISED SHIFT RAIL)

MODELS: 1992-94 CHEVROLET AND GMC TRUCK C/K 1-3 AND P3 MODELS EQUIPPED WITH NV4500 (RPO MT8) 5-SPEED MANUAL TRANSMISSION

CONDITION:

SOME OWNERS MAY COMMENT THAT THE SHIFT LEVER MAY STICK IN OVERDRIVE OR REVERSE OR THE SHIFT LEVER MAY BE BLOCKED OUT OF OVERDRIVE OR REVERSE.

TO PROPERLY DIAGNOSE THIS CONDITION, THE TRANSMISSION SHOULD REMAIN ASSEMBLED AND IN THE VEHICLE. USE THE CLUTCH DURING ALL SHIFT SEQUENCES AND BE SURE THE TRANSMISSION TEMPERATURE IS THE SAME AS WHEN THE CUSTOMER EXPERIENCES THE CONDITION. FOLLOW THE STEPS LISTED BELOW TO DETERMINE IF THE TRANSMISSION HAS THIS CONDITION.

1. START THE ENGINE WITH THE TRANSMISSION IN NEUTRAL. 2. SHIFT THE TRANSMISSION INTO REVERSE AT IDLE SPEED. IF THE TRANSMISSION SHIFTS INTO REVERSE, SHIFT BACK INTO NEUTRAL. IF THE TRANSMISSION SHIFTS INTO NEUTRAL, SHIFT BACK INTO REVERSE, BACK-UP THE VEHICLE APPROXIMATELY ONE FOOT AND REPEAT THE SHIFT SEQUENCE. 3. REPEAT THE ABOVE PROCEDURE SEVEN TIMES. IF THE SHIFT EFFORT BECOMES EXTREMELY HIGH OR THE LEVER STICKS OR IS BLOCKED-OUT AT ANY TIME, THIS CONDITION IS PRESENT AND REPAIRS ARE REQUIRED. IF THE CONDITION DOES NOT OCCUR, PROCEED TO THE NEXT STEP. 4. WHILE DRIVING THE VEHICLE ON THE ROAD, SHIFT INTO OVERDRIVE AND BACK TO NEUTRAL. 5. REPEAT THE ABOVE PROCEDURE SEVEN TIMES. IF THE SHIFT EFFORT BECOMES EXTREMELY HIGH OR THE LEVER STICKS OR IS BLOCKED-OUT AT ANY TIME, THIS CONDITION IS PRESENT AND REPAIRS ARE REQUIRED.

CAUSE:

THE OVERDRIVE SHIFT FORK (FIGURE 2, #137) IS INDEXED UPWARD TOO MUCH. THIS PUSHES THE OVERDRIVE SPEED SYNCHRONIZER SLEEVE (#132) UPWARD CAUSING IT TO BIND TO THE OVERDRIVE CLUTCH GEAR (#134).

CORRECTION:

STARTING FEBRUARY 2, 1994 ALL TRANSMISSIONS ARE BEING BUILT WITH REVISED INDEXING OF THE OVERDRIVE SHIFT RAIL (#139). THIS REVISED INDEXING WILL ROTATE THE OVERDRIVE SHIFT FORK DOWNWARD 1 DEGREE. THE O/D SYNCHRONIZER ASSEMBLY SHOULD ALSO BE REPLACED.

SERVICE PROCEDURE:

REMOVE THE TRANSMISSION FROM THE VEHICLE FOLLOWING DIRECTIONS IN THE APPROPRIATE SERVICE MANUAL, SECTION 7B, MANUAL TRANSMISSION, TRANSMISSION REPLACEMENT. REFER TO THE APPROPRIATE UNIT REPAIR MANUAL (SECTION 7B2, NEW VENTURE GEAR 4500 MANUAL TRANSMISSION) FOR UNIT DISASSEMBLY AND ASSEMBLY. FOLLOW THE PROCEDURES LISTED TO:

1. REMOVE THE SHIFT COVER ASSEMBLY AND THE REAR (EXTENSION) OIL COVER FROM THE TRANSMISSION. 2. REMOVE THE OVERDRIVE SHIFT RAIL / FORK ASSEMBLY FROM THE CASE. 3. INSTALL THE REVISED OVERDRIVE SHIFT RAIL / FORK ASSEMBLY. 4. INSTALL A NEW O/D SYNCHRONIZER ASSEMBLY. 5. INSTALL THE REAR (EXTENSION) OIL COVER AND SHIFT COVER ASSEMBLY TO THE TRANSMISSION.

THE FOLLOWING PARTS ARE NOT REUSABLE AND MUST BE REPLACED EVERY TIME THEY ARE REMOVED:

1. MAINSHAFT NUT 2. REAR (EXTENSION) OIL COVER BOLTS 3. OVERDRIVE CLUTCH GEAR SNAP RING 4. SHIFT FORK-TO-RAIL RETAINING PINS 5. OVERDRIVE SHIFT FORK

THE FOLLOWING FASTENER TIGHTENING SPECIFICATIONS SHOULD BE USED:

1. SHIFT COVER-TO-CASE BOLTS 28 N.M (21 LBS. FT.) 2. REAR (EXTENSION) OIL COVER-TO-CASE BOLTS 54 N.M (40 LBS. FT.) 3. VIBRATION DAMPER MOUNTING NUT (4WD) 441 N.M (325 LBS. FT.) 4. YOKE ASSEMBLY MOUNTING NUT (2WD) 441 N.M (325 LBS. FT.)

THE FOLLOWING SEALANTS SHOULD BE USED FOR REASSEMBLY:

1. P/N 1052942 ANAEROBIC SEALANT -SHIFT COVER-TO-CASE -REAR (EXTENSION) OIL RETAINER-TO-CASE 2. P/N 12346004 PIPE SEALANT WITH TEFLON: -DRAIN AND FILL PLUGS -PTO COVER BOLTS

IMPORTANT: THIS TRANSMISSION REQUIRES A SPECIAL SYNTHETIC LUBRICANT. DO NOT SUBSTITUTE ANY OTHER LUBRICANT AS INTERNAL TRANSMISSION DAMAGE MAY RESULT. TRANSMISSION CAPACITY IS 3.78L (4 QUARTS). 12346074 1 QUART CONTAINER 12345871 1 GALLON CONTAINER

SERVICE PARTS INFORMATION:

P/N DESCRIPTION QTY 12548394 OVERDRIVE RAIL 1 12547836 OVERDRIVE FORK 1 12540300 SYNCRONIZER, O/D 1 12542972 PIN 3 15635274 RETAINING RING 1 15635285 BOLT, REAR RETAINER 8 12544824 NUT, MAINSHAFT, C1,2,3 W/O 1 TRANS MOUNTED PARK BRAKE 15659372 NUT, MAINSHAFT, C1,2,3 WITH 1 TRANS MOUNTED PARK BRAKE 15635327 NUT, MAINSHAFT, K1,2,3 1 1052942 LOCTITE(R) 518 SEALANT A/R 12346004 PIPE SEALANT W/TEFLON A/R 12345871 FLUID, MANUAL TRANS (1 GALLON) A/R 12346074 FLUID, MANUAL TRANS (1 QUART) A/R

PARTS ARE CURRENTLY AVAILABLE FROM GMSPO.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OP DESCRIPTION MODEL LABOR TIME K2767 5TH FORK, AND/OR SHAFT REPLACE C 3.0 HRS. K 3.4 HRS. P 3.6 HRS.

FIGURES: 2

CAPTIONS: FIGURE 1 - NV4500 TRANSMISSION IDENTIFICATION INFORMATION FIGURE 2 - NV4500 OVERDRIVE COMPONENTS

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 1994 GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.