The transmission in a vehicle matches the power requirements of the automobile to the power output available from an engine or motor; the automatic transmission’s selection of different gears keeps the engine operating in speed ranges that allow high levels of efficiency to be achieved. Most modem transmissions operate at efficiencies of over 85 percent on the city cycle and 92 to 94 percent on the highway cycle. The efficiency losses that do occur are caused primarily by: Hydraulic losses in the torque converter (current automatic transmissions use a hydraulic system to transmit the engine power to the drivetrain). Designs…
