Section 7 (Electronics - Design And Function - 4 Of 4): Transmission: Overview
WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2013 Volvo C70, 2012 Volvo C70, 2011 Volvo C70, 2010 Volvo C70, and 2009 Volvo C70. However, it is still accessible from the selected car via links, so may be relevant.
AW55-51 is a 5 speed electronically controlled automatic transmission with a lock-up function for the three highest gears. The transmission control module (TCM) adapts the gear changes to ensure that the correct gear is selected for the driving mode, engine load, driver requirements, speed etc. This gives good fuel economy combined with increased comfort by ensuring smoother gear changes and lower noise levels.
In a vehicle with an automatic transmission, the driver neither needs to decide which gear should be used nor shift gear. There is a operating system in the AW55-51 which uses a torque converter and gear shift system to do this.