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How to Control When the TCC Engages on a 3T40

The torque converter clutch (TCC) is controlled by a small solenoid valve on a GM 3T40, a three-speed transmission. The TCC kicks in when the engine is in third gear. It allows the engine to reduce its revolutions per minute while still maintaining speed. It is a version of the "overdrive" in older transmissions. Most of this control is done by an on-board computer that you cannot adjust. But there is one simple cable adjustment you can perform yourself to change when the TCC engages.

Instructions

1

Check the transmission fluid under the hood. If it is low, fill it to the required mark.

2

Grab a large cable that passes over the left side of the engines air intake. It should be beside the place that states the engines cubic inches in bold letters on top of the valve covers.

3

Slide your fingers around a large button connector where the cable turns and begins to turn down. Push the button on the side of the connector. When you find the button, place a small C-clamp around the connector and button to hold the button closed.

4

Pull on the cable slightly to release the tension. Remove the C-clamp. Reach down past the bracket that holds the cable and grab the throttle valve. It is spring-loaded nut behind the bracket. Pull back on it slightly with your fingers. If you cant pull hard enough on it, slip a 1/2-inch wrench over it and pull on it and the wrench together, but do not turn the wrench. Just use if for leverage.

5

Pull on the cable until it makes several clicking sounds as it adjusts. Release the nut.