REVISED: TORQUE CONVERT.CLUTCH DIAGNOSIS INFORMATION

Some 1982 and 1983 THM 125C transmissions may experience a torque converter shudder condition immediately following the torque converter engagement. Other suspected causes for this condition could be one or more of the items listed below. Inspect for the following conditions along with those specified in Chevrolet Bulletins 83-I-23 and 82-T-125.

1. An incorrectly machined seal groove on the turbine shaft in the transmission. A step in the bottom corners of the seal groove (Figure 1) will prevent the P.T.F.E. seal from contacting the side wall of the groove, and will not seal. If this condition is found, replace the turbine shaft and seals. Follow service manual procedures for installing and sizing the seals.

2. Particles of gasket material sticking the torque converter clutch apply valve or plugging the converter release orifice in the control valve spacer plate. If a torn gasket is found, remove the gasket material from either the converter clutch apply valve or the control valve spacer plate. Replace the torn gasket, with a new gasket, but first remove area marked (in Figure 2), by carefully cutting with a knife.

3. An intermittent incorrect signal from the vehicle speed sensor (V.S.S.). D rt or grease on the magnet field plate in the V.S.S. might be sending an early signal so that the converter clutch engages early. Remove the V.S.S. and clean it.

4. A leak between the turbine shaft I.D. and inner turbine shaft sleeve. If all of the items above have been performed and the condition still exists, replace the turbine shaft.

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.