NEW DESIGN FORWARD CLUTCH ASSY 125 TRANSMISSION

EARLY PRODUCTION 1982 CIMARRONS EQUIPPED WITH THM 125C TRANSMISSIONS MAY EXPERIENCE A HARSH GARAGE SHIFT FEEL WHEN THE TRANSMISSION IS SHIFTED FROM THE NEUTRAL (OR PARK) POSITION TO REVERSE AND/OR FROM THE NEUTRAL (OR PARK) POSITION TO DRIVE. THESE TWO CONDITIONS ARE SEPARATE AND CAUSED BY THE OPERATION OF UNRELATED COMPONENTS. THIS BULLETIN OUTLINES THE PRODUCTION CHANGES AND SERVICE PROCEDURES WHICH WILL PROVIDE A MORE DESIRABLE GARAGE SHIFT FEEL. I.HARSH NEUTRAL (OR PARK) TO REVERSE SHIFT THE LISTED DESIGN CHANGES WERE IMPLEMENTED IN PRODUCTION TO CORRECT THIS CONDITION. A.THE LO AND REVERSE PISTON WAS MODIFIED, ELIMINATING THE NEED FOR AN APPLY RING. B.THE CLUTCH PLATE NEXT TO THE LO AND REVERSE PISTON WAS CHANGED TO A WAVED STEEL PLATE, ELIMINATING ONE FLAT STEEL CLUTCH PLATE. C.THE LO AND REVERSE CLUTCH HOUSING FEED ORIFICE WAS REDUCED IN SIZE. VEHICLES EXHIBITING THIS CONDITION MAY BE CORRECTED USING THE FOLLOWING PROCEDURE: 1.REPLACE THE PAST DESIGN LO AND REVERSE HOUSING ASSEMBLY WITH THE NEW DESIGN LO AND REVERSE HOUSING P/N 8643921 (REFER TO FIGURES 1 AND 2). 2.REPLACE THE PAST DESIGN LO AND REVERSE CLUTCH PISTON AND APPLY RING ASSEMBLY WITH THE NEW DESIGN ONE PIECE ASSEMBLY P/N 8643922 (REFER TO FIGURE 2). 3.REPLACE THE FLAT STEEL CLUTCH PLATE NEXT TO THE LO AND REVERSE PISTON ASSEMBLY WITH A WAVED STEEL PLATE P/N 8637574 (REFER TO FIGURE 2). II.HARSH NEUTRAL (OR PARK) TO DRIVE ENGAGEMENT FEEL THE LISTED FORWARD CLUTCH DESIGN CHANGES WERE IMPLEMENTED IN PRODUCTION TO CORRECT THIS CONDITION. A) THE FORWARD CLUTCH PISTON WAS REDESIGNED (REFER TO FIGURE 3, VIEWS B AND C, ITEM 1), ELIMINATING THE APPLY RING (VIEW A, ITEM 1). B) THE BACKING PLATE WAS MADE SELECTIVE TO CONTROL PISTON TRAVEL (REFER TO FIGURE 3, VIEWS B AND C, ITEM 2). REFER TO THE SERVICE SECTION OF THIS BULLETIN FOR PROPER SELECTION PROCEDURE. C) THE FORWARD CLUTCH FEED ORIFICE WAS REDUCED IN SIZE (REFER TO FIGURE 3, VIEWS B AND C, ITEM 3) AND AN OIL DISPLACEMENT INSERT WAS ADDED (VIEW C, ITEM 4). THESE TWO CHANGES WILL PRODUCE A MORE DESIRABLE NEUTRAL TO DRIVE ENGAGEMENT FEEL. D) THE CHECK BALL CAPSULE (REFER TO FIGURE 3, VIEW B, ITEM 5) WAS REMOVED (VIEW C, ITEM 5) AND TWO (2) EXHAUST HOLES WERE ADDED TO THE NEW FORWARD CLUTCH PISTON (VIEW C, ITEM 6). WHEN THE PISTON IS APPLIED THE EXHAUST HOLES WILL SEAL AGAINST THE WAVED STEEL CLUTCH PLATE (VIEW C, ITEM 7). WHEN THE PISTON IS RELEASED, APPLY OIL WILL EXHAUST BETWEEN THE WAVED STEEL CLUTCH PLATE AND THE PISTON. TRANSMISSIONS EXHIBITING THIS CONDITION MAY BE CORRECTED USING THE FOLLOWING PROCEDURE: 1.REPLACE THE PAST OR INTERIM DESIGN FORWARD CLUTCH ASSEMBLY WITH THE NEW DESIGN FORWARD CLUTCH ASSEMBLY. SELECT ONLY THOSE PARTS SPECIFIED FOR THE NEW DESIGN CLUTCH LISTED BELOW. FORWARD CLUTCH ASSEMBLY SERVICE PART NUMBERS NAME FORWARD CLUTCH HOUSING NEW DESIGN 8637645 NAME FORWARD CLUTCH PISTON & SEALS NEW DESIGN 8637973 NAME FORWARD CLUTCH PISTON SEALS NEW DESIGN 8631986 NAME FORWARD CLUTCH PISTON INSERT NEW DESIGN 8631986 NAME SELECTIVE BACKING PLATE #1 NEW DESIGN 8637883 NAME SELECTIVE BACKING PLATE #2 NEW DESIGN 8637884 NAME SELECTIVE BACKING PLATE #3 NEW DESIGN 8637885 2.DETERMINE THE PROPER SELECTIVE BACKING PLATE REQUIRED FOR THE FORWARD CLUTCH ASSEMBLY USING THE FOLLOWING PROCEDURE: A) INSERT FEELER GAGE STOCK BETWEEN THE SELECTIVE BACKING PLATE AND THE SNAP RING. B) THE END PLAY, WITHOUT COMPRESSING THE WAVED CLUTCH PLATE, MUST BE 1.0-1.5MM (.040"-.070"). C) IF THE END PLAY IS NOT WITHIN SPECIFICATIONS, SELECT THE PROPER BACKING PLATE FROM THE FORWARD CLUTCH END PLAY CHART (REFER TO FIGURE 4). FOR POSITIVE IDENTIFICATION, MEASURE THE THICKNESS OF THE SELECTIVE BACKING PLATE. NOTICE: USE OF A NEW DESIGN FORWARD CLUTCH HOUSING WITHOUT PROPER END PLAY WILL CAUSE EXCESSIVE CLUTCH PLATE WEAR.

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.