A/T - 125C Uncontrolled Lock-Up, Kills Engine At Stop

TRANSMISSION: 125C

BULLETIN: # 048

SUBJECT: Lock-up

APPLICATION: GM

DATE: May 1991

125C Uncontrollable Lock-up (It Kills The Engine At A Stop)




If you have a 125C that kills the engine when you come to a stop, you have a restricted solenoid, auxiliary valve body cross leaks or both.

Step 1: If you're working on a unit that is earlier than 1987, replace the solenoid with # 8652379. The early type of solenoid would clog easier than the late type.

Step 2: Always flat sand the auxiliary valve body & cover.

Step 3: Make sure you're using the right auxiliary valve body gasket. See figures below.




Note
See figure 2 for auxiliary valve body ID.

An 84-86 model will have no cup plug and it will have a three land valve. An 87 and later valve body will have a two land valve.




Step 4: Make a .010-.020 cut in the gasket to exhaust some of the signal oil. See figure 3.


BULLETIN RECAP:

During A Rebuild

^ I.D. the auxiliary valve body and use the proper gasket.

^ Flat sand the auxiliary valve body and cover.

^ Make sure the solenoid isn't restricted. If it's a 1988 or earlier model, replace the solenoid.

FOR ADDITIONAL INFORMATION:

See May 1991 Transmission Digest "Technically Speaking"