NEW PARKING BRAKE MECHANISM (BRAKE DRUM AT REAR OF TRANS.)

SUBJECT: NEW 1989 HJA MODEL AUTOMATIC TRANSMISSION FOR P TRUCK MOTOR HOME WITH 14,500 LB GVWR

MODELS: 1989 P3 WITH THM 475/HYDRA-MATIC 3L80.HD

THIS BULLETIN HAS BEEN REVISED TO CORRECT MODEL INVOLVED AND REPLACES GMC TRUCK SERVICE BULLETIN 89-T-40 ALL COPIES OF WHICH SHOULD BE DISCARDED.

BULLETIN COVERS:

A new 1989 HJA model automatic transmission for 7.4L carb, (P3 Truck) motor home chassis, 14,500 lb GVWR (Gross Vehicle Weight Rating), was released. The information contained in this bulletin lists the parts that are new, and deleted, along with correct assembly, and disassembly procedures that are not contained in the Unit Repair Section. The deleted parking mechanism parts are replaced by a brake drum which is located at the rear end of the transmission.

DATE OF PRODUCTION CHANGE: (Figure 1) ------------------------- November 1, 1988 (Julian Date 305) production began building the 475/3L80-HD HJA model.

NEW PART:

New Converter Assembly - 8650904 (Brazed Converter Pump)

Parts are currently available from GMSPO.

DELETED PARTS: (Figure 2) ------------- Pawl - Parking Lock - 8633060

Shaft - Parking Lock Pawl - 8624976

Retainer - Parking Pawl Shaft - 148148

Spring - Parking Pawl Retum - 8623041

Bracket - Parking Lock - 8624112

Bolt - Hex HD (5/16-18 X.62) - 179814 or 179816

Actuator Asm - Parking Lock - 8624091

SERVICE ACTION:

When servicing 1989 THM 475/HYDRA-MATIC 3L80-HD HJA model, it is important to follow the procedures in this bulletin during disassembly and assembly of the Detent Lever and Manual Shaft.

Transmission Disassembly:

Detent Lever and Manual Shaft Remove or Disconnect (Figure 2)

1. Nut (703) and Pin (704).

2. Detent Lever (707).

3. Plug (709).

4. Shaft (705) and Seal (706).

Transmission Assembly:

Detent Lever and Manual Shaft

Inspect:

Detent Lever (707) for damage or cracks Manual shaft for damage

Install or connect (Figure 2)

1. Plug (709).

2. Detent Lever (707).

3. Manual Shaft (705) and Seal (706).

4. Nut (703) on Shaft (705).

5. Pin (704).

SERVICE MANUAL REFERENCE:

Please record this information in any 1989 THM 400/475 Unit Repair Section of the Service Manual.

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.