DIRECT CLUTCH DISTRESS CAUSE & CORRECTION OUTLINED

Subject: DIRECT CLUTCH DISTRESS

Model and Year: 1985-90 C, K, P, R, V TRUCKS AND G VAN WITH 3L80 AND 3L80-HD AUTOMATIC TRANSMISSION

TO: ALL CHEVROLET DEALERS

BULLETIN COVERS:

Some HYDRA-MATIC 3L80/3L80-HD models experienced Direct Clutch distress. This distress was caused by an oil leak in the clutch apply circuit at the Center Support joint between the Case and the Center Support. A new Center Support (654), Case Assembly (10), Piston (650) and Bolt (79) eliminated this root cause for Direct Clutch distress.

DATE OF PRODUCTION CHANGE: (Figure 1)

Beginning March 1, 1990 (Julian Date 060) all 1990 HYDRA-MATIC 3L80/3L80-HD transmissions were built with the new Center Support (654), Case Assembly (10), Intermediate Piston (650) and Bolt (79).

SERVICE PROCEDURE: (Figure 2)

IMPORTANT: Use new bolt (79) only with new support (654) and new piston (650). Use new piston (650) only with new support (654). Use new support assembly (654) in previous case (1 0) only with previous bolt (79). Use new case (1 0) only with new support (654), new piston (650) and new bolt (79). Do not reuse old Center Support (654).

Torque bolt (79) to 32 lbs. ft. (43 N.m) and assure the bolt head (79) is seated to the bottom of the case (1 0).

IMPORTANT: DO NOT USE NEW BOLT (79) WITH PREVIOUS CASE (10).

SERVICE PARTS INFORMATION: (Figure 3)

Service Description Package Models ----------- ------- ------- Pkg - Case Assembly (Light Truck) 8629990 See Figure 3 Pkg - Case Assembly (Heavy Truck) 8629991 See Figure 3 Pkg - Support, Race, Plug, Piston & Bolts 8629994 All

Parts are currently available from GMSPO.

SERVICE MANUAL REFERENCE:

Refer to the Unit Repair section of the appropriate Service Manual for the proper Pump Bushing and Seal replacement procedures.

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.