SERVICE MANUAL UPDATES 440T4 TRANSAXLE NEW PISTON

SUBJECT: PRELIMINARY DIAGNOSIS AND DESCRIPTION OF NEW TRANSAXLE MODEL AND 2ND CLUTCH DISTRESS ON 1WSH MODEL

MODELS AFFECTED: 1991 REGAL

BULLETIN COVERS:

Two Hydra-Matic 4T60 (THM 440T4) transaxle models were introduced for 1991 Regals with 3800 EV6 engine (VIN Code L). The 1991 Regal was initially built with the 1WSH model. However, the 1WWH model has replaced the 1WSH model and includes a new molded 2nd clutch piston and seal, 2nd clutch housing (to accommodate the new piston), tapered apply plate for the 2nd clutch, valve body and spacer plate (Figures 1 and 2). Refer to figures 3 and 4 for fluid pressure and shift speed information when diagnosing these transaxle models.

IMPORTANT:

Do not try to update a previous model transaxle with the new molded piston 2nd clutch assembly - the new assembly is calibrated differently. If the 2nd clutch fails on a 1WSH model, replace the transaxle with a 1WWH SRTA model.

SERVICE MANUAL REFERENCE:

Refer to the following information when servicing a 1991 1WSH or 1WWH model transaxle. All other instructions and procedures are the same as published in the 1990 Service Manual. Refer to the appropriate Automatic Transaxle Diagnosis section in the 1990 Service Manual for information not covered in this bulletin.

SERVICE PROCEDURE: (Figure 5)

Installation of the new molded 2nd clutch piston into the new 2nd clutch housing requires the use of a newly designed seal protector and installer, J38678 (includes detail 1 and 2). The tool will be available in the 1991 dealer essential tool package.

SERVICE PARTS INFORMATION:

When servicing the 1WWH model, use the service parts listed below. When the 1WSH model requires replacement, replace the unit with a 1WWH model SRTA transaxle.

Part Number Description Model Usage ------ ------------------- ----------- 8676929 (SRTA) Transaxle As Shipped (with new 1WWH, 1WSH 2nd clutch)

8651919 Pkg, Housing, Drum and Bushing Assembly, 1WWH 2nd Clutch

8676387 Piston, Molded Seal, 2nd Clutch 1WWH

8675319 Apply Ring and Release Spring Assembly, 1WWH 2nd Clutch

8675227 Plate, Apply Reaction 1WWH

8677626 Plate Assembly, Valve Body Spacer 1WWH

8677629 Body Assembly, Control Valve 1WWH

8675958 Pkg, Overhaul Seals & Gasket 1WWH

8675959 Pkg, Overhaul Repair Complete 1WWH

Parts are currently available from GMSPO.

LINE PRESSURE CHECK

Line pressure is controlled by pump output to the pressure regulator valve and is boosted in Reverse and Dl by the reverse boost valve.

Also, line pressures should increase with throttle opening due to a decrease in engine vacuum supply to the vacuum modulator.

Line pressures will boost to a maximum pressure if the T.V. cable is disconnected at the throttle body and pulled to its full travel. This method of checking pressures WILL NOT provide accurate line pressure as referenced in the chart below.

CHECK PRESSURES IN THE FOLLOWING MANNER:

Minimum Line Pressure Check

- Disconnect and plug vacuum supply at modulator. - Apply 61 kPa (18 in. Hg.) vacuum to modulator with pump (B). - Set parking brake and apply vehicle brakes. - Take pressure readings in all gear ranges with engine running at proper R.P.M. - Compare pressures with information provided in the chart below.

Full Line Pressure Check

- Have 0 kPa (0 in. Hg.) vacuum to modulator. - Set parking brake and apply vehicle brakes. - Take pressure readings in all gear ranges with engine running at proper R.P.M. - Compare pressures with information provided in the chart below.

NOTICE: Total running time not to exceed 2 minutes.

CAUTION:

Brakes must be applied at all times.

1991 HYDRA-MATIC 4T60 SHIFT SPEED CHART

MODEL FINAL DRIVE 1-2 MIN 2-3 MIN 3-4 MIN 4-3 PART 3-2 PART RATIO THROTTLE THROTTLE THROTTLE THROTTLE THROTTLE -------- --------- --------- -------- -------- -------- -------- WWH, WSH 06 3-16 2-24 43-52 56-65+ 43-50

MODEL FINAL DRIVE 4-3 COAST 3-2 COAST 2-1 COAST RATIO DOWN DOWN DOWN ------- ------------ --------- --------- ---------

WWH, WSH 06 40-50 17-20 10-14

NOTES:

1. ALL SPEEDS INDICATED ARE IN MILES PER HOUR. CONVERSION TO Km/h = MPH x 1.609.

2. SHIFT POINTS WILL VARY SLIGHTLY DUE TO ENGINE LOADS AND VEHICLE OPTIONS.

3. SPEEDS LISTED WITH + EXCEED 65 MPH.

Figure 4 - Shift Speed Chart

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.