APPLICATION: This SAE Information Report details some of the equipment and procedures used to measure critical characteristics of hydraulic fluids used in automatic shift transmission current at the time of this revision. These transmissions characteristically use a torque converter and planetary gear type drive. The fluid used in passenger car@ light truck@ and school bus automatic transmission must perform in five distinct functions. These are: 1. Hydrodynamic energy transmission medium for use in the torque converter. 2. Hydrostatic energy transmission medium for use in the hydraulic control-logic circuits and for servomechanisms. 3. Lubricating medium for shaft bearings@ thrust bearings@ and involute or spur gear load surfaces. 4. Sliding-friction energy transmission medium for use with lubricated bands and clutches. 5. Heat transfer medium with liquid- or air-cooled systems for maintenance of a suitable automatic transmission temperature range.