SUPPLEMENTAL DIAGNOSIS 440-T4 ROUGH SHIFT, TCC SHUDDER, ETC.

Models Affected: 1984-85 Century and 1985 Electra

Accurate diagnosis is essential to determine if a transaxle can be corrected by procedures which do not require an exchange unit.

An updated THM 440-T4 diagnosis section is included in the 1985 Buick Chassis Service Manual, Vol. II. Further diagnostic information is as follows:

No Upshift

A. Governor - Cause may be an imprex particle under governor ball. Imprex is an impregnation plastic used to seal cases against porosity.

When the engine is shut off, the particle may float back into the governor feed passage and then lodge again in the governor when engine is restarted. To correct this condition, remove the governor, reinstall the governor cover and operate the engine in drive range to flush the oil passages. Clean the governor. To verify that the cleaned governor is operable, seat the balls by holding the governor weights against them. Pour solvent into the governor shaft and inspect for leakage past the balls. If no leakage is noted, reinstall governor.

B. Leakage at governor oil pipe retainer; loose or stripped retainer bolt.

C. Valve body - 1-2 shift valve train may be stuck in valve body. Remove any burrs or raised metal on valves with a flat hone stone. DO NOT remove any more metal from valve than necessary. 1-2 valve is an aluminum alloy. Inspect TV valve for freeness.

The valve body can be removed and replace without removing the transaxle from the car. Use care to catch check balls during removal.

TCC Shudder

A. A rolled or cut TCC accumulator piston seal.

B. Turbine shaft seals cut or damaged.

C. TCC solenoid "O" ring cut or broken. On-car service.

Intermittent No Drive or No Drive At All

Input sprag failure.

Erratic Shifts, Rough Shifts,Slipping Shifts, 2nd Gear Starts

A. Vacuum related conditions. Refer to Dealer Technical Bulletin 85-7440-5.

B. A vacuum line that is pinched or kinked may cause vacuum to be retained in the modulator, resulting in law pressure and possible second clutch distress. If fluid inspection indicates a burned clutch an exchange unit is recommended. Replace vacuum line.

C. A vacuum problem may result in No. 10 check ball peening into the spacer plate seat. Leakage at No. 10 check ball may influence shift quality or TCC operation. On-car correction is recommended if the clutch is not burned.

1st Gear Shudder

May also exhibit:

- Slip or second gear start - Slip or flare on 2-3 shift - Flare/freewheel in 3rd on liglit acceleration - No drive, reverse OK

Leak at 1-2 servo apply or release pipe to valve body or case seal.

No Forward Gear

No forward gear - Slips all ranges. Input clutch may be burnt.

Input accumulator piston cocking in bore. The input accumulator piston is located on the case side on the channel plate.

Shudder on 3-4 Shift

Turbine shaft "O" ring cut or missing.

TCC on at Stops

Engine Stall - May have a valve body knockout slug lodged in TCC apply valve; TCC apply valve locked in apply position.

Fluid Burned, Slips in Second

Pinched vacuum line holding vacuum in modulator causing low pressure and a burned second clutch. Exchange unit recommended. Replace vacuum line.

3-2 Downshift Abrupt or Harsh - 1985 Model Only

Replace 3-2 downshift spring in valve body. Spring is available by contacting Buick Technical Assistance Communication System. The spring can be installed without removing the valve body. This correction does NOT apply to 1985 1/2 models.

Whine Noise

A whine or whistle noise under acceleration may be due to:

- Low fluid level

- Filter to case seal leak

- Leak at filter crimp

NOTE: Due to thermo-element operation, fluid level after a refill will require rechecking after warm operation such as a road test to ensure that transaxle is adequately filled.

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.