TRANS CASE FRACTURE (INSTALL NEW PARK BRAKE SPRING ). GMC Truck GMC MD Steel Tilt 76.2" 1992

SUBJECT: TRANSMISSION CASE FRACTURE (INSTALL NEW PARK BRAKE SPRING RETURN, LEVER, BACKING PLATE AND BRACKET)

MODELS: 1992-93 CHEVROLET AND GMC TRUCK W5, W6, W7 WITH ALLISON AT542/AT545 AUTOMATIC TRANSMISSIONS (RPOS MT9 AND MF1)

CONDITION:

TRANSMISSION CASE FRACTURE.

CAUSE:

TRANSMISSION CASE FRACTURE MAY OCCUR IF THE PARK BRAKE IS APPLIED WHILE THE VEHICLE IS IN MOTION.

SERVICE PROCEDURE:

INSTALL NEW PARK BRAKE LEVER AND BACKING PLATE.

REMOVAL:

1. SECURELY BLOCK VEHICLE WHEELS AND RELEASE THE PARKING BRAKE. 2. LOOSEN THE JAM NUT (FIG 2, ITEM 1) AND ADJUSTER NUT (FIG 2,ITEM 2) ON THE PARKING BRAKE CABLE, AND DISCONNECT THE CABLE. 3. LOOSEN THE NUTS ON THE PROPELLER SHAFT, THEN DISCONNECT THE PROPELLER SHAFT. 4. LOOSEN THE LOCK BOLT (FIG 3, ITEM 1) INSIDE THE FLANGE, REMOVE THE LOCK PLATE (FIG 3, ITEM 2), LOOSEN THE FIXING BOLT (FIG 3, ITEM 3) AND REMOVE THE WASHER FLANGE (FIG 3, ITEM 4) AND DRUM. 5. LOOSEN AND REMOVE THE FOUR (4) BOLTS (FIG. 4) THEN REMOVE THE PARKING BRAKE. 6. REMOVE THE PARKING BRAKE PARTS IN THE ORDER OF THE NUMBERS (FIG.5, ITEMS 1-7).

IMPORTANT: WHEN REMOVING THE SPRING, USE A SPRING INSTALLER/REPLACER (FIG. 6).

7. REMOVE THE PARKING CONTROL CABLE FROM THE BRACKET AND REMOVE THE BRACKET FROM THE TRANSMISSION BY REMOVING THE BOLTS ATTACHED TO THE BRACKET (FIG. 7).

REPLACEMENT:

1. REPLACE THE SPRING RETURN, LEVER, SUPPORT PLATE AND BRACKET WITH NEW PARTS (FIG. 1, ITEMS 1, 2, 3 AND 4). 2. ASSEMBLE ALL PARKING BRAKE PARTS IN THE ORDER OF THE NUMBERS (FIG 8, ITEMS 1-7).

IMPORTANT: WHEN INSTALLING THE SPRING, USE A SPRING INSTALLER/REPLACER (FIG. 6).

3. ATTACH THE FOUR PARKING BRAKE BACK PLATE ASSEMBLY TO TRANSMISSION BOLTS (FIG. 4), TIGHTENING BOLTS 16.3 - 21.7 N.M (12-16 LBS. FT.). 4. ATTACH THE PARKING BRAKE CABLE BRACKET TO THE TRANSMISSION (FIG.9) TIGHTEN BOLTS 8.1 - 10.8 N.M (6.0-8.0 LBS. FT.). 5. ATTACH THE FLANGE AND DRUM ASSEMBLY TO THE TRANSMISSION. INSTALL THE WASHER FLANGE (FIG 3, ITEM 4) THEN THE FIXING BOLT (FIG 3, ITEM 3) TIGHTENING 18.3 - 22.4 N.M (13.5 - 16.5 LBS. FT.). INSERT THE LOCK PLATE (FIG 3, ITEM 2) INTO ITS LOCATION AND TIGHTEN BOLT (FIG 3, ITEM 3) AS NECESSARY TO ALIGN BOLT HOLE. INSTALL BOLT (FIG 3,ITEM 1) AND TIGHTEN TO 0.8 - 1.4 N.M (0.6 TO 1.0 LBS. FT.). 6. ATTACH THE PROPELLER SHAFT TO FLANGE. TIGHTEN TO THE FOLLOWING TORQUE SPECIFICATION:

FLANGE BOLT SIZE TORQUE

M12-1.259.5 15.6 N.M (11.5 LBS. FT.) M14-1.614.2 23.6 N.M (17.4 LBS. FT.)

7. ATTACH THE PARKING BRAKE CABLE TO THE BRACKET (FIG. 10). TIGHTEN 5.4 - 7.3 N.M (4.0 TO 5.4 LBS. FT.). 8. ADJUST THE LINING GAP OF PARKING BRAKE ACCORDING TO SERVICE MANUAL. CHECK THAT THE GEAR SELECT LEVER IS IN NEUTRAL, AND JACK UP THE BACK WHEELS. TURN THE PROPELLER SHAFT, SO THE ADJUSTING HOLE OF BRAKE DRUM IS ALIGNED WITH THE POSITION OF ADJUSTER (FIG. 11). 9. INSERT A SCREWDRIVER IN THE ADJUSTING HOLE OF DRUM, AND TURN THE ADJUSTER UNTIL IT DOES NOT MOVE UPWARDS. THEN, BACK OFF THE ADJUSTER FROM THIS POSITION BY 13 NOTCHES (FIG. 12). MEASURE THE LINING GAP, IT SHOULD BE APPROXIMATELY 0.25 MM (0.01 IN.). 10. PULL THE PARKING LEVER IN THE DIRECTION AS ILLUSTRATED (FIG. 10), AND MOUNT THE CABLE IN THE POSITION WHERE THE FIRST TOUCH IS FELT.

IMPORTANT: BE SURE TO FASTEN THE ADJUSTER NUT IN A PLACE OF FIRST TOUCH, AND FIX WITH JAM NUT. THE SECOND TOUCH IS WHERE THE LINING IS IN CONTACT WITH THE DRUM.

11. PULL THE PARKING BRAKE LEVER IN THE CAB, AND CONFIRM THAT THE PULLING ALLOWANCE IS OF 3 TO 8 NOTCHES.

SERVICE PARTS INFORMATION:

P/N DESCRIPTION QTY

94050122 SPRING LEVER RETURN 1 94050240 LEVER 1 94050236 PLATE; SUPPORT 1 94050241 BRACKET; PARK BRAKE CONTROL 1

OBTAIN PARTS FROM AMERICAN ISUZU PARTS DISTRIBUTION NETWORK (AIPDN).

WARRANTY INFORMATION:

LABOR OP DESCRIPTION LABOR TIME

H2860 LEVER AND/OR SUPPORT, PARKING BRAKE USE PUBLISHED ASSEMBLY - R+R OR REPLACE LABOR OPERATION TIME

FIGURES: 12

CAPTIONS: FIGURE 1 - PARK BRAKE LEVER, SPRING, SUPPORT PLATE AND BRACKET FIGURE 2 - JAM AND ADJUSTER NUT FIGURE 3 - LOCK BOLT, LOCK PLATE, FIXING BOLT AND WASHER FLANGE FIGURE 4 - PARK BRAKE BOLTS FIGURE 5 - PARK BRAKE DISASSEMBLY SEQUENCE FIGURE 6 - SPRING INSTALLER/REPLACER FIGURE 7 - PARK BRAKE CONTROL CABLE BRACKET FIGURE 8 - PARK BRAKE ASSEMBLY SEQUENCE FIGURE 9 - PARK BRAKE CABLE TO TRANSMISSION FIGURE 10 - PARK BRAKE CABLE TO BRACKET FIGURE 11 - ALIGNING BRAKE DRUM ADJUSTING HOLE WITH ADJUSTER FIGURE 12 - ADJUSTING PARK BRAKE

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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.