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Introduction to the Hyrdamatic 6L80

The Hydra-Matic 6L80 is the first member of a new family of fully automatic, six-speed, clutch-to-clutch, rearwheel drive, electronic-controlled transmissions that General Motors will be offering.

The transmission consists primarily of a four-element torque converter, an integral fluid pump and converter housing, a single and double planetary gear set, friction and mechanical clutch assemblies, and a hydraulic pressurization and control system.

The four-element torque converter contains a pump, a turbine, a pressure plate splined to the turbine, and a stator assembly. The torque converter acts as a fluid coupling to smoothly transmit power from the engine to the transmission. It also hydraulically provides additional torque multiplication when required. The pressure plate,when applied, provides a mechanical "direct drive" coupling of the engine to the transmission.

The planetary gear sets provide the six forward gear ratios and reverse. Changing gear ratios is fully automatic and is accomplished through the use of a Transmission Control Module (TCM) located inside the transmission. The TCM receives and monitors various electronic sensor inputs and uses this information to shift the transmission atthe optimum time.

The TCM commands shift solenoids and variable bleed pressure control solenoids to control shift timing and quality.

The TCM also controls the apply and release of the torque converter clutch which allows the engine to deliver the maximum fuel efficiency without sacrificing vehicle performance. All the solenoids, including the TCM, are packaged into a self-contained control solenoid valve assembly

The friction components used in this transmission consist of five multiple disc clutches. The multiple disc clutches combine with one mechanical sprag clutch to deliver seven different gear ratios (six forward and one reverse) through the gear sets. The gear sets then transfer torque through the output shaft.

The control solenoid (with body and TCM) valve assembly, or solenoid assembly, is perhaps the most unique

component in the 6L80 transmission. The solenoid assembly attaches directly to the upper and lower valve body

assemblies and utilizes a lead frame design which connects all the electrical control components to the TCM, thus

eliminating the need for an internal wiring harness. The TCM, shift solenoids, pressure control solenoids,

transmission fluid pressure (TFP) switches and the transmission fluid temperature (TFT) switch are all integrated

into the solenoid assembly. Because of this integrated design, these electrical control components will not be

serviced separately, even though the components may be diagnosed separately. The fluid passages to the switches and solenoids are protected from debris by a filter plate assembly.