INTERMITTENT OR NO DRIVE OR REVERSE (MAY BE SPRAG OR RACE)

Model and Year: 1984-86 CELEBRITY MODELS WITH THM 440-T4

Intermittent or complete loss of drive and reverse on a 1984 to 1986 vehicle equipped with a THM 440-T4 transaxle having normal line pressures may be caused by the input sprag clutch assembly. This condition may be corrected by installing a new (wider) input sprag clutch assembly and related parts.

Effective April 1, 1986, (Julian Date 091) Figure 1, all 1986 THM 440-T4 transaxles were built using a new input sprag clutch assembly. Effective May 1, 1986 (Julian Date 121), all Service Replacement Transmission Assembly (SRTA) models were built using the new input sprag clutch assembly.

SERVICE ACTION: (Figures 2 and 3)

1. Remove the transaxle from the vehicle and disassemble it to the point of removing the input sprag clutch assembly (653). - Complete disassembly of the transaxle is not always necessary.

2. Bench check the operation of the sprag and third roller clutch assembly as shown in Figure 2.

3. Inspect the input sprag clutch assembly (653) for: - Mispositioned sprag elements. - Broken ribbon tabs (between the sprag elements).

4. Disassemble the input sprag clutch assembly (Figure 3) and inspect for: - Cracked inner or outer races (#650, #654). - Indentation marks on the inner race (#650) that would indicate sprag element "rollover".

Replace the input sprag clutch assembly if any of the conditions described above are present. Use the appropriate service part(s) referred to in the "Service Parts" section below.

SERVICE PARTS:

A. When replacing the input sprag clutch assembly on a transaxle built before April 1, 1986 (Julian Date 091) use the following service part number:

Part Number Contents ----------- -------- 8646986 (1) Input Sprag Clutch Assembly (2) Snap Rings (1) Input Sprag clutch Outer Race (1) Input Sprag Clutch Inner Race (2) Input Sprag Clutch Wear Plate

B. When replacing the input sprag clutch assembly on a transaxle built on or after April 1, 1986 (Julian Date 091) use the following service part number:

Part Number Contents ----------- -------- 8646985 (1) Input Sprag Clutch Assembly (wider sprag) (2) Snap Rings (1) Input Sprag Clutch Outer Race (wider) (1) Input Sprag Clutch Inner Race (wider)

C. To update a transaxle built before April 1, 1986 (Julian Date 091) or a SRTA transaxle built before May 1, 1987 (Julian Date 121) to use the new (wider) input sprag clutch assembly, the transaxle must contain the following three new design parts as shown in Figure 4 (replace as required based on the content/ Julian Date of the transaxle):

1. Part #8658368, lube dam (695) effective March 6, 1985 (Julian Date 065)

2. Part #8658407, final drive sun shaft (669) effective February 19, 1985 (Julian Date 050) - Counter bore added to assembly with lube dam.

3. Part #8658408, output shaft (565) effective February 19, 1985 (Julian Date 050) - chamfer removed to assemble with lube dam.

NOTICE: These three correct design parts must be installed for proper lubrication of the third roller clutch and new design sprag assemblies.

After these parts have been assembled into the unit, the new input sprag clutch assembly (653) and input carrier assembly (662), contained in the service package listed below, may be used:

Part Number Contents ----------- -------- 8662906 (1) Input Sprag Clutch Assembly (wider) (2) Snap Rings (1) Input Sprag Clutch Outer Race (wider) (1) Input Sprag Clutch Inner Race (wider) (1) Input Sprag Clutch Retainer (narrower) (1) Input Sun Gear Spacer (wider) (1) Input Carrier Assembly Complete (narrower hub)

Refer to the THM 440-T4 (ME9) Automatic Transaxle Unit Repair Table of Contents in the appropriate Service Manual for input sprag clutch assembly service information.

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.