The torque converter is a key component in any automatic transmission: it aids starting and takes on the job of the conventional clutch by connecting and seperating the engine and transmission. It is the interaction between the engine with its mechanical kinetic energy and the torque converter with its hydraulic energy generated by special oil that gives the transmission the capacity for automatic driving. In other words, the torque converter functions like a clutch in a manual transmission.
For SACHS spare parts various catalogs are available as PDF for download free of charge, e.g. the SACHS shock absorber or the SACHS clutch catalog.