UNIT REPAIR TRANS. THM 440T4 3-2 SHIFT CONTROL VALVE CHANGE

MODELS AFFECTED: ALL 1985 FWD DEVILLE/FLEETWOOD MODELS (EQUIPPED WITH GAS ENGINE)

Effective with VIN broadcast number 314311, gas engine equipped 1985 FWD De Villes and Fleetwoods have been released with both a later model THM 440-T4 automatic transaxle and ECM PROM calibration to improve shift feel and pleasability. As a result, the specific parts and service information contained in this bulletin must be utilized when performing transaxle service on these vehicles.

EARLY TRANSAXLE MODEL replaced by LATER TRANSAXLE MODEL --------------------- ----------- ---------------------

AC (Limousine) AF AY (FED & CAL) AM

Models OY and OB for diesel applications are not affected by this change.

Parts Information:

The hydraulic circuits in the control valve assembly, channel plate, spacer plate have been redesigned in later model units. As a result, these components are not interchangeable. When servicing the transaxle, check the I.D. nameplate (refer to Figure 1) to determine the transaxle model year and type. GMWDD catalogues (printed after June, 1985) utilize this number (e.g., 5AY or 5AM) to distinguish early and late components.

Although the listed components CANNOT be interchanged between early and late transaxle models, complete transaxle assemblies can be interchanged. Later model assemblies (AM/AF) are to be utilized when transaxle assembly exchange is required.

When an early model THM 440-T4 is replaced with a later model, install a later calibration ECM PROM. Refer to the following PROM information to ensure correct application.

TRANS MODEL EMISSIONS TYPE PART NUMBER PROM I.D. BROADCAST CODE ----- -------------- ------------ --------- -------------- AF, AM Federal 16052276 215 HMC AF, AM California 16052282 226 HMD

Repair Information:

The current 1985 Service Information Manual describes early models and will provide enough reference material when performing dealer authorized repairs for both early and late models (for details concerning dealer authorized repairs refer to Serviceman Bulletin T-85-77). The exception is check ball locations. Refer to Figure 2 for control valve assembly and Figure 3 for channel plate check ball locations for the later transaxles (AM/AF). Note the position and size of check ball #5 has been changed from that of early models.

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.