SERVICE INFO. & PACKAGES DISTRESSED 4TH CLUTCH
MODELS AFFECTED: All 1989 - 1990 WITH HYDRA-MATIC 4T60 (THM440T4)
This bulletin cancels and replaces Corporate Bulletin 977163.
BULLETIN COVERS: (Figures 1 through 4)
New channel plate assembly, inside detent lever and manual valve service packages for distressed 4th clutch.
IMPORTANT: 4th Clutch distress may be caused by the manual valve being positioned between the neutral and D4 position. This allows the input clutch to be applied in 4th gear. The input clutch will try to drive the input sun gear while the 4th clutch is trying to hold the sun gear. A mispositioned manual shaft may be caused by excessive drag or friction in the range selection system. Contributors to excessive drag include an improperly routed or binding shift cable and interference between the column and dashboard contact surfaces. This excessive drag condition may also contribute to a misadjusted shift cable during setting. Also, a mispositioned shift indicator needle may cause an owner to "line-up" the needle in the D4 or OD position and not allow the manual valve to fully position in the D4 or OD range. Or an owner that rests his/her hand on the shifter of a console shift model may also be inadvertently pushing the shifter toward the neutral position.
IMPORTANT: Possible early signs of 4th clutch distress include a leak from the left axle seal (channel plate side) and/or side cover to channel plate gasket. The six side cover to channel plate gasket nuts may also have no torque. The heat generated from the 4th clutch slipping when applied would cause the axle seal and garter spring to expand, causing a leak, and also damage the gasket, leaving the nuts loose. Other possible early signs may include shudder in 1st gear, slips in all gears and burned transaxle fluid.
A distressed 4th clutch vehicle may not move in drive and reverse. This is due to the 4th clutch assembly being melted or friction welded to the channel plate. This may lock the 4th clutch hub to the channel plate, causing a tie-up condition when the input clutch is applied. The input clutch is applied in Park, Reverse, Neutral and Drive ranges at 0 MPH. The vehicle can be pushed with the engine off (when not in park) but when the engine is started, the vehicle will not move.
For the new service packages, the following parts were modified:
- New inside detent lever (704) will have the manual link hole location changed for a different "throw" of the manual valve. The previous and new inside detent lever are not interchangeable even though the parts will physically assemble. The new inside detent lever must be used with the new manual valve and channel plate. The previous inside detent lever must be used with the previous manual valve and channel plate. The identifier for the new "W" car inside detent lever is an added square hole. The previous "W" car inside detent lever is gold in color. Some of the early new "W" car inside detent levers may be gold in color and have the added square hole. The gold color will be discontinued and the square hole will be the only identifier for the new "W" car inside detent lever. The previous inside detent lever will still be available for models that just need replacement of the lever for 1987 and prior model years.
- New manual valve (403) will have changes to the valve lands and be reduced 0.25mm (0.010") in diameter for the new porting changes to the service channel plate. The previous and new manual valves are not interchangeable. The new manual valve will assemble into the previous channel plate but the transaxle will not function because of excessive leakage due to the differences in sizes.
- New channel plate (404) will have porting changes for the new manual valve and new inside detent lever. The porting changes will help ensure that two ports will never be opened at once to cause distress to the 4th clutch assembly when the shift cable is not set correctly or is kinked or binding. The bore for the new manual valve will be reduced to accommodate the manual valve. This will make the new and previous parts non-interchangeable. The new manual valve and inside detent lever must be used with the new service channel plate. Only the new service channel plate will be available for 1985-1/2 through 1990 models.
NOTICE: The new service channel plate assembly must be used with the new manual valve and new detent lever. Using the previous inside detent lever and the new service channel plate or the new inside detent lever and the previous channel plate will cause durability concerns.
DATE OF PRODUCTION CHANGE
Suspect HYDRA-MATIC 4T60 (THM 440-T4) transaxles were built from January 2, 1989 (Julian Date 002) through January 15, 1990 (Julian Date 016) with the "E" channel plate shown in figure 4.
On January 16, 1990 (Julian Date 016) a new channel plate, manual valve and inside detent lever will be used in production that incorporate all the changes listed in this Service Bulletin. The new channel plate for production will not have an input accumulator bore (the service channel plate will still have the input accumulator bore). A wave plate and extra input clutch plate will be added to the input housing input clutch that will replace the function of the input accumulator. These changes will be addressed in another Service Bulletin.
SERVICE PROCEDURE
Order service parts from the "Service Parts Information" section of this bulletin. Also, check and/or correct the items listed below:
- Other conditions known to cause 4th clutch distress also include: damaged 3-4 accumulator piston seal, loose channel plate torx head bolt (72), leaking driven sprocket, 4th clutch piston seals or missing #1 check ball from a previous repair or leaking #5 check ball.
NOTICE: When repair of a distressed 4th clutch has been completed, it is essential to inspect and set the shift cable according to the procedures as outlined in the transaxle on-vehicle service section of the appropriate service manual. To ensure proper cable set, place the driver lever (shift lever inside the passenger compartment) against the reverse side of the neutral gate in the column or console prior to setting the cable at the transaxle.
SERVICE NOTES
The manual valve link (401) and rod end retaining spring (manual valve) (402) have not been revised for this change.
SERVICE PARTS INFORMATION
IMPORTANT: If the previous channel plate assembly is ordered for a 1985-1/2 through 1990 model, the order will be superseded to a new service channel plate assembly package that will service the transaxle model. A 1985-1/2 through early 1986 models will require the slot for the inside detent lever to assemble the manual valve link. Order package 8668991 that will contain a new manual valve link that will assemble to the new inside detent lever.
The new service channel plate assembly packages will contain:
- Channel plate assembly - Valve, manual - Lever, inside detent
Part Model Number Description Year Model Usage ------ ----------- ---- ------------ 8668993 Channel Plate Asm.-Complete 1989-90 AAH, ACH, ABH, ADH, AFH, AHH, AJH, ANH, ATH
8668994 Channel Plate Asm.-Complete 1989-90 LMH, LNH, CLH, CPH, CZH, YPH, YCH, YJH
8668996 Channel Plate Asm.-Complete 1989-90 CHH, YKH, CJH, YLH, CDH, CYH, YAH, YFH
8668997 Channel Plate Asm.-Complete 1990 LAH
*8668995 Channel Plate Asm.-Complete 1989-90 BAH, WBH, BDH, WCH, BFH, WLH, BHH, WRH, BJH, WZH, BPH, WTH, BWH, WUH, PAH, PBH, VXH, VYH
*IMPORTANT: Also, order and install with package 8668995 one of the two packages listed below for the following 1990 models OBAH, OBDH, OBFH, OBHH, OBPH, OBWH and OBJH with two plate 4th clutch assemblies built from July 10, 1989 (Julian Date 191) to July 31, 1989 (Julian Date 212) of the 1990 Model Year.
8668980 Package - Single Plate 4th Clutch 1990 OBAH, OBDH, OBFH - Plate Assembly, 4th Clutch - Plate, 4th Clutch Apply - Plate, 4th Cl. Reaction (2 in Pkg.) - Bushing/Valve 1-2 Accumulator - Instruction Sheet
8668981 Package - Single Plate 4th Clutch 1990 OBHH, OBPH, - Plate Assembly, 4th Clutch OBWH, OBJH - Plate, 4th Clutch Apply - Plate, 4th Cl. Reaction (2 in Pkg.) - Bushing/Valve 1-2 Accumulator - Instruction Sheet
8668991 Pkg. Lever - Inside Detent 1985-90 All Models Except (for new channel plate) W-Carline with New Service or Production Channel Plate
8668992 Pkg. Lever - Inside Detent 1988-90 W-Carline Only (for new channel plate) That Has New Service or Production Channel Plate
8646958 Pkg. Lever - Inside Detent 1985-90 All Models Except (for previous channel plate) W-Carline with Previous Channel Plate
Parts are currently available for part numbers 8668980, 8668981 and 8646958.
All other parts are expected to be available on 2-16-90. Until then, normal part orders will not be accepted by GMSPO. Only verifiable emergency VIP orders will be accepted. SPO will make every effort to obtain parts. All parts will be placed on 400 control to waive VIP surcharges. However, the part will be shipped premium transportation at dealer's expense. All other order types will be canceled as incorrectly ordered while the 400 control is in place.
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.
