A/T - Harsh Park/Neutral to Reverse Engagement
89Chevy24Number: 88-421-7A
Section: 7A
Date: August 1989
Subject: HARSH PARK OR NEUTRAL TO REVERSE ENGAGEMENT
Model and Year: 1987-88 B CAR WITH THM 200-4R TRANSMISSION
TO: ALL CHEVROLET DEALERS
This bulletin covers service parts for a 1987 or 1988 THM 200-4R transmission exhibiting a harsh Park or Neutral to Reverse engagement. The "reverse engagement package," a new spacer plate and 1-2 accumulator housing assembly are available for service. The spacer plate and accumulator housing function as a Reverse accumulator to soften Reverse engagement.
Figure 1 - THM 200-4R Transmission Identification Information:
DATE OF PRODUCTION CHANGE: (Figure 1)
All THM 200-4R models built after March 14, 1988 (Julian date 074), were built with the new Spacer Plate and 1-2 Accumulator Housing Assembly.
Figure 2 - 1-2 Accumulator Assembly:
SERVICE PROCEDURE: (Figure 2)
To service a 1987 or 1988 THM 200-4R CCF, CHF, CRF, CTF, CYF, CZF, KCF, KJF, KTF model exhibiting a harsh reverse engagement (built prior to March 14, 1988), replace the spacer plate and 1-2 accumulator housing assembly with the appropriate parts listed under "Service Parts Information."
Figure 3 - Typical Spacer Plate:
Figure 4 - 1-2 Accumulator Housing Assembly:
To identify the "reverse engagement" spacer plate and 1-2 accumulator housing:
^ The new spacer plate has a round hole (indicated by the arrow in Figure 3); the previous spacer plate had a rectangular hole in that location.
^ The new 1-2 accumulator housing contains a checkball and sleeve assembly (refer to Figure 4).
SERVICE PARTS INFORMATION:
Part Number Description Model
8657755 1-2 Accumulator Housing Assembly 7CCF, 7CHF, 7CRF, 7CTF
8634969 Spacer Plate Gaskets (Pkg. of 2) 7CYF, 7CZF, 7KJF, 7KTF
8634166 1-2 Accumulator Housing to 8CCF, 8CHF, 8CRF, 8CTF
Accumulator Plate Gasket 8CYF, 8CZF, 8KTF
8669050 Spacer Plate (Identification: CD) 7CRF, 7CTF, 8CRF, 8CTF
8669060 Spacer Plate (Identification: CH) 7KCF, 7KJF, 7KTF, 8KTF
8669051 Spacer Plate (Identification: CE) 7CCF, 8CCF
8669049 Spacer Plate (Identification: CC) 7CHF, 8CHF
8669052 Spacer Plate (Identification: CF) 7CYF, 8CYF
8669047 Spacer Plate (Identification: CA) 7CZF, 8CZF
Parts are currently available from GMSPO.
Transmissions built after implementation of the reverse engagement package, March 14, 1988, can be serviced with individual components available through GMSPO. Refer to the GMSPO catalog for part numbers.
SERVICE MANUAL REFERENCE:
Refer to the Unit Repair section of the THM 200-4R service manual for spacer plate and 1-2 accumulator service information.