NEW DESIGN FORWARD CLUTCH ASSY 125 TRANSMISSION

Recently changes were made in the forward clutch assembly to produce a more desirable neutral to drive engagement feel and eliminate the check ball capsule. These changes were accomplished in two (2) steps. See Figure 1.

Step 1 - Interim Design - Beginning July, 1981

(a) The forward clutch piston was redesigned (View B, Item 1), eliminating the apply ring (View A, Item 1).

(b) The backing plate was made selective to control piston travel (View B, Item 2). Refer to the service section of this bulletin for proper selection procedure.

Step 2 - New Design - Beginning September, 1981

(a) The forward clutch feed orifice was reduced in size (View B & C, Item 3) and an oil displacement insert was added (View C, Item 4). These two (2) changes will produce a more desirable neutral to drive engagement feel.

(b) The check ball capsule (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.

(c) A selective backing plate is used to control piston travel (View C, Item 2).

SERVICE INFOFMATION

(1) The following chart contans the service part numbers which are affected by these design changes.

FORWARD CLUTCH ASSEMBLY SERVICE PART NUMBERS

Name Past Design Interim Design New Design

Forward Clutch Housing 8631926 8631926 8637645 Forward Clutch Piston & Seals 8631985 8637973 Forward Clutch Piston & Apply Ring 8631921 Forward Clutch Piston Seals 8631986 8631986 8631986 Forward Clutch Piston Insert 8637605 Backing Plate 8631027 Selective Backing Plate #1 8637883 8637883 Selective Backing Plate #2 Figure 2 8637884 8637884 Selective Backing Plate #3 8637885 8637885

(2) When servicing the individual parts:

(a) identify the forward clutch assembly design.

(b) Select only those parts specified for each design.

(3) End play procedure for selective backing plate:

(a) Insert feeler gage stock between the selective backing plate and the snap ring. See Figure 2.

(b) The end play, without compressing the waved clutch plate, must be 1.0mm - 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. See Figure 3 for positive identification measure the thickness of the selective backing plate.

(d) 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.