This SAE Recommended Practice was prepared by the SAE Fuels and Lubricants Technical Committee: (a) to assist the designers and users of heavy-duty transmissions in the selection of powershift transmission fluids for field use and (b) to promote a uniform practice for use by marketers of lubricants and equipment builders in identifying and recommending these fluids by type. This classification is designed for fluids used in heavy-duty truck, bus, earthmoving, and marine transmissions or steering clutches. The fluids must perform the following five functions: 1. Transmit hydrodynamic energy in a torque converter. 2. Transmit hydrostatic energy in hydraulic circuits. 3. Lubricate bearings, bushings, gears, and moving parts. 4. Provide proper frictional properties in lubricated bands and clutches. 5. Provide heat transfer medium for liquid- or air-cooled systems to maintain suitable operational temperature range.