VEHICLE APPLICATIONS: 1989-90 A, C, E, H, K, W, V
This bulletin cancels and replaces Bulletin 90-7440-108 dated 02/15/90.
Bulletin Covers: (Figures 1 through 4)
New channel plate assembly, inside detent lever and manual valve service packages for distressed 4th clutch.
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 colour. Some of the early new "W" car inside detent levers may be gold in colour and have the added square hole. The gold colour will be discontinued and the square hole will be the only identifier for the new "W" car inside detent leverl. 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.
Suspect HYDRA-MATIC 4T60 (THM 44-T4) and THM F-7 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.
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.
The manual valve link (401) and rod end retaining spring (manual valve) (402) have not been revised for this change.
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, 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.
Part Model Number Description Year Model Usage ------ ----------- ---- ----------- 8668980 Package - Single Plate 4th Clutch 1985-90 OBAH, OBDH, -Plate Assembly, 4th Clutch OBFH -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 (for new channel plate) Except W-Carline with New Service or Production Channel Plate
8668992 Pkg. Lever - Inside Detent 1985-90 W-Carline (for new channel plate) Only That Has New Service or Production Channel Plate
8646958 Pkg. Lever - Inside Detent 1985-90 All Models (for previous channel plate) Except W Carline with Previous Channel
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.