NO TCC RELEASE 125C AUXILIARY VALVE BODY GASKET

During September, 1983 all THM 125-C transmissions were built with a new auxiliary valve body and valve body gasket. The new auxiliary valve body does not have an orifice plug hole (Figure 1). The auxiliary valve body gasket is made out of a new material and has three holes made larger (Figure 2).

The changes to the gasket eliminate a no torque converter clutch release (TCC) or no TCC apply condition that resulted from incorrect cup plug, mispositioned cup plug or eroding gasket.

NOTE: The only interchangeable part is the auxiliary valve body cover (Figure 3). The new auxiliary valve body gasket must be used with the new auxiliary valve body. The past auxiliary valve body gasket must be used with the past auxiliary valve body.

When servicing any model THM 125-C transmission auxiliary valve body refer to the following procedure:

1. Identify the auxiliary valve body being serviced (past or new). See Figure 1.

2. If the past auxiliary valve body is being serviced refer to Chart 1. If

CHART 1

PART BEING REPLACED PART NUMBER ------------------- ----------- Auxiliary Valve Body Cover Gasket 8653947 Auxiliary Valve Body Cover 8643645 Auxiliary Valve Body Orifice Plug 8623796 Auxiliary Valve Body (past design not serviced) New auxiliary valve body must be used, order Service Package 8653946.

CHART 2

PART BEING REPLACED PART NUMBER -------------------- ------------ Auxiliary Valve Body Cover Gasket 8643863 Auxiliary Valve Body Cover 8643645 Auxiliary Valve Body Models BF, BL, CE, CA, CB, CF, CL, CK, CT, CC, PE, PD, PG, PJ, PW, PF 8653946 Service Package EM, EN, EW, HC, HS, HV, HY, OP 8653945 Service Package

Service Package 8653946 contains:

1 8643865 Auxiliary Valve Body 1 8643863 Gasket Aux. Valve Body 1 8643645 Cover Aux. Valve Body

Service Package 8653945 contains:

1 8643864 Body Auxiliary Valve 1 8643863 Gasket Aux. Valve Body Cover 1 8643645 Cover Aux. Valve Body

Only the Auxiliary Valve Body Cover, Auxiliary Valve Body Cover Gasket, and Auxiliary Valve Body Orifice Plug can be ordered separately.

When servicing any auxiliary valve body inspect it for erosion around hole number 1 in Figure 2. If the gasket is eroded then replace the auxiliary valve body cover along with the required gasket.

If the auxiliary valve body being serviced needs the orifice plug replaced due to damage or missing follow the procedure listed below.

A. If the orifice plug is still in the auxiliary valve body, remove it with a 7/32 screw extractor.

B. Install a new orifice plug (Part Number 8623796) using a 5/16" punch to start the orifice plug in the hole. Then use a 3/8" punch and seat the plug flush with the wall figure 1.

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.