reliable and so rugged it was widely used in drag racing during the 1960s. It was not as smooth as some competitors' transmissions (notably Buick's Dynaflow), but was more efficient, especially at highway speeds. The Hydra-Matic paved the way for widespread acceptance of automatic shifting. A 3-speed light-duty version of the Turbo Hydra-Matic, called the Turbo-Hydramatic 180 was produced by GM's Hydra-Matic division from 1981 to 1998 for use in a wide variety of small cars and trucks. Hydramatic is a trade name for GM's automatic transmission division, which produces a variety of transmissions, the most notable of which is the Turbo Hydra-Matic from the 1960s to the 1990s. Design The Hydramatic used a two-element fluid coupling (not a torque converter, which has at least three elements, the pump, turbine, and stator although Roto Hydra-Matic has a fluid coupling and a fixed stator) and three planetary gearsets, providing four forward speeds plus reverse. Standard ratios for the original Hydra-Matic were 3.82:1, 2.63:1, 1.45:1, and 1.00:1 in automotive applications, and 4.08:1, 2.63:1, 1.55:1, and 1.00:1 in light truck and other commercial applications. The Controlled-Coupling Hydra-Matic used 3.97:1, 2.55:1, 1.55:1, and 1.00:1. Roto Hydramatic 375; a three-speed, four-range automatic has a 3.56:1, 2.93:1, 1.56:1, and 1.00:1. Roto Hydramatic 240; a three-speed, four-range automatic has ratios of 3.64:1, 3.03:1, 1.57:1, and 1.00:1 The Hydramatic was fitted with two pumps to pressurize its hydraulic control system and provide lubrication of internal components. The front pump was a variable displacement vane unit driven from the fluid coupling housing, which meant oil pressure would be available immediately upon starting the engine. Relatively constant pressure was maintained by moving a slide inside the pump, which had the effect of changing the pump's displacement and therefore the volume of oil being delivered. The rear pump was an unregulated gear pump driven from the transmission output shaft, which meant it was capable of pressurizing the transmission if the vehicle was in motion. This feature made it possible to push-start a vehicle with a dead battery if the vehicle could be accelerated to at least . At higher speeds, the rear pump provided all the oil volume that was needed to operate the transmission and the front pump's slide was nearly centered, causing that pump to produce little output. In first gear, power flow was through the forward planetary gear assembly (either 1.45:1 or 1.55:1 reduction, depending on the model),