BURNED FWD, OVERRUN/3-4 CLUTCH USE SOLID TURBINE SHAFT SEALS

MODELS: ALL 1987 LIGHT DUTY MODELS AND 1988 C/K MODELS WITH THM 700-R4 AUTOMATIC TRANSMISSIONS

BULLETIN COVERS:

New, solid (not "scarf cut" - Figure No. 1) turbine shaft seals, service tools, procedures and parts. Information in this bulletin is not included in your 1987 Service Manual.

DATE OF PRODUCTION/SRTA CHANGE: (Figure No. 2)

By October 6, 1986 (Julian Date 279) all 1987 THM 700-R4 production and Service Replace- ment Transmission Assembly (SRTA) models were built with solid turbine shaft seals.

SERVICE ACTION

Solid turbine shaft seals must be used on all 1987 THM 700-R4 transmissions produced with Auxiliary Valve Bodies. If "scarf cut" seals are used on a 1987 model with an auxiliary valve body assembly, a condition of burned forward, overrun or 3-4 clutches can occur. Both types of turbine shaft seals can be used on a 1982 through 1986 THM 700-R4 transmission but solid seals are recommended on all models.

Installation and sizing of solid turbine shaft seals is done with Kent-Moore tools J-36418-1 and J-36418-2 (Figure No. 3). The Kent-Moore sizing tool J-36418-2 needs to be altered at the flanged end of the tool. The instruction sheet that comes with the tool shows to use the tool with the flanged end down. The flange must be removed to allow the tool to size the bottom seal ring. Alter the Kent-Moore sizing tool using the following procedure:

1. Place the sizing tool in a vise (Clamp flange in vise jaws). 2. Cut the flanged end off at the bottom of the tool as shown in Figure No. 4. 3. File any rough edges until smooth. 4. Size each seal ring after installation onto the turbine shaft. 5. Size all seal rings just prior to installation of pump assembly as shown in Figure No. 5.

Replacement tools will be sent to all applicable dealerships at no cost when alterations have been completed.

SERVICE PARTS INFORMATION:

Solid turbine shaft seals are not included in Overhaul Kits Part Number 8649965 (Seals and Gaskets) and 8649960 (Complete). Seals can be ordered separately and are installed from the factory on a service 1987 model input housing and shaft assembly.

Part Number Description

8667035 Solid Turbine Shaft Seals (4 Required)

SERVICE MANUAL REFERENCE:

The 1987 Service Manual procedures can be used to remove and install the Input Housing and Shaft Assembly. Use the information in this bulletin to service the Turbine Shaft Seals.

SERVICE NOTES:

IMPORTANT: Also use the information in Truck Service Bulletins 87-T-28 and 87-T-45 when overhauling a 1987 THM 700-R4 transmission.

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.