A/T - Harsh Park/Neutral to Drive Engagement
Number: 87-151Section: 7A
Date: MAY, 1987
Subject: HARSH PARK/NEUTRAL TO DRIVE ENGAGEMENT
Model and Year: 1981-87 VEHICLES WITH THM-200-4R TRANSMISSIONS
Figure 1 - THM 200-4R TRANSMISSION IDENTIFICATION INFORMATION:
Figure 2 - FORWARD CLUTCH ASSEMBLY:
TO: ALL CHEVROLET DEALERS
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.
April 25, 1986 (Julian date 115 refer to figures 1 and 2), these changes were introduced for all THM 200-4R models.
Forward clutch assembly, minus check ball in housing (618) Forward clutch piston assembly (622) Additional waved plate (666) Front internal gear (633)
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 below.
Part Number Description
8639943 Neutral Drive Shift Package (Contains
Forward Clutch Assembly Complete, Front
Internal Gear and Thrust Washer)
Transmissions built after April 25, 1986 (Julian date 115) can be serviced with separate parts, refer to the current GMSPO catalog.
Important: When servicing the forward clutch, select the correct backing plate (627). Backing plate selection affects piston travel, shift feel and clutch durability.
Figure 3:
Figure 4:
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 0.7 mm - 1.5 mm (0.028"-0.059"). Refer to Figure 4 for backing plate identification information.
NOTICE: 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).