Brief description FA 57: Notes
Automatic transmission FA 57 is an electronically controlled 5 stage automatic transmission with lock-up function and facility to shift manually.
The FA 57 is principally constructed around 4 planetary gear units, disc clutches, torque converter with lock-up coupling, hydraulic control system and an electronic control system.
The gearbox is controlled by a control module (TCM), which continuously processes information from its own sensors as well as from other control modules. On the basis of this processed information, it controls the transmission hydraulic system.
The FA 57 has the following advantages over conventional hydraulic transmission:
- Improved shifting performance and smoother shifting as torque is reduced when shifting takes place.
- Reduced mechanical stresses on the entire drive train due to torque limitation.
- Improved fuel economy thanks to driving programs optimizing fuel consumption as well as lock-up in 3rd, 4th and 5th gears. To improve fuel economy further, the lock-up clutch is allowed to slip. This means that a difference of 50 and 200 RPM is permitted between the engine speed and the input shaft speed. This is only permitted at low engine loads. The engine then pulls for longer with slipping lock-up and the transmission does not need to disengage lock-up (transfer power through the torque converter). Slipping lockup is the primary reason for a high-grade transmission fluid. If the temperature of the transmission fluid rises, a temperature-dependent program is automatically selected, protecting the gearbox from heat damage. See TEMPERATURE SENSOR, TRANSMISSION FLUID .
- Possibility to choose between driving programs: Normal, Sport and Manual.
- Self-diagnosis and storage of diagnostic trouble codes.
- TCM sends and receives information from other control modules in the car via analogue signals and bus communication, see BUS AND DIAGNOSTICS COMMUNICATION .