It is known fact that all 4L80E transmissions make use of electronic controls. In most occasions, it is from the Powertrain Control Module (PCM). Some machines are equipped with shift maps that can be selected by the driver depending on the usage. A part of the strategy involved in using PCM is the shift stabilization, which can significantly reduce hunting. The torque converter that is used in numerous factory applications can be controlled by using a PWM lockup solenoid. That being said, there are still a large part of the performance enthusiast community who like to reprogram the 4L80E built transmission in order to operate as a straightforward on-off solenoid. About fifteen years ago, the H1 received a 4L80E, fitted with a dedicated T42 transmission system. The transmission was also equipped with a much enhanced Park/Neutral safety switch. After that, other GM applications started to follow.
TCM or Transmission Control Module can be considered to be an adaptive learning (integrated with a computer system) fitted into the transmission’s valve body. This can communicate with the ECM or Engine Control Module by using the vehicle bus network. This is the departure from previously used automotive control systems that many earlier electronic transmissions utilized as a separate control module. At present, the high-speed CAN network permits high rate of data sharing in between the units so that a major collaboration can be made in between the engine and transmission systems. Since the 4L80E build transmissions are often times used in conversion applications with previously used non-PCM controlled setups, GM and numerous aftermarket control modules are needed to take control of the transmission operation.
The 4L80E transmission mostly features two speed sensors (turbine input speed and output speed). It makes use of the Input Speed Sensor (ISS) so that input speeds can be compared with the engine speed. With the help of this data, shift speeds can be easily adjusted under detectable conditions. The PCM can be used to command the engine so that momentary drop power can be detected during an intense shift. Clutch line pressures and grade braking are additional great features that can be activated by haul/tow mode.
Since the transmission needs a special speed signal for shift control, conversion installers need to be aware of the different configuration set that are present. The 4L80E build transmissions that were produced in between 1991 and 1996 feature a speed sensor case’s rear portion (driver’s side), and that is applicable for both 2WD and 4WD applications. For the later produced versions, the rear sensor can be omitted as the data can be found in the transfer case output shaft. For the specific requirement of some adaptations, this eliminated sensor and its internal reluctor ring may be required to be installed for proper operation.