NEW DESIGN FORWARD CLUTCH SMOOTHER PK./NEUT. TO DRIVE

MODELS AFFECTED: ALL 1981-1987 THM 200-4R (NW9) EQUIPPED VEHICLES (EXCEPT FOR 1986-87 BRF, 1984-85 BQ, AND 1983 BR MODELS)

BULLETIN COVERS

A 1981 through 1987 vehicle equipped with a THM 200-4R transmission may have a harsh PARK/NEUTRAL to DRIVE engagement feel. A new design "feed/bleed" system for the forward clutch gives more cushioning during forward clutch apply. This system can be used in most THM 200-4R applications to reduce a harsh DRIVE engagement feel.

DATE OF PRODUCTION CHANGE: (Figures 1 and 2) ------------------------- April 25, 1986 (Julian date 115), these changes were introduced for all THM 200-4R models (except model BRF):

Forward Clutch Assernbly, minus check ball in housing (618) Forward Clutch Piston Asseinbly (622) Additional waved plate (666) Front internal gear (633)

SERVICE ACTION

If a vehicle equipped with a THM 200-4R transmission, built prior to April 25, 1986 (Julian date 115), has a harsh Park/Neutral to Drive engagement, install the Service Package listed in Service Parts Information.

Models built after April 25, 1986 (Julian date 115), can be serviced with separate parts.

NOTICE: This system CANNOT be used on 1986-1987 BRF, 1984-1985 BQ, and 1983 BR models.

IMPORTANT: When servicing the forward clutch, select the correct backing plate (627). Backing plate selection affects piston travel, shift feel and clutch durability.

Backing plate selection: (Clutch fully assembled) Apply an evenly distributed load in the direction indicated in Figure 3 to remove slack from the clutch assembly. Use 20 lbs. (9 kg) of pressure against the backing plate--excessive pressure will cause an inaccurate measurement. With the clutch assembly compressed, use a feeler gage to measure the distance between the backing plate and snap ring. Correct backing plate travel is 0.7mm-1.5mm (0.028"-0.059"). Refer to Figure 4 for backing plate identification information.

SERVICE PARTS INFORMATION

PART NUMBER DESCRIPTION ----------- ------------ 8639943 Neutral Drive Shift Package (Contains Forward Clutch Assembly, Complete; Front Internal Gear and Thrust Washer)

Parts available separately: 8657257 Forward Clutch Assembly, Complete 8639947 Front Internal Gear and Thrust Washer (Can be used on ALL model years.)

SERVICE NOTES

Earlier design front INTERNAL GEARS (Service Package Number 8630909) CANNOT be used with THM 200-4R models built after April 25, 1986 (Julian date 115).

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.