providing a very efficient engine brake. According to the Chevrolet manual, above 65 mph at wide open throttle, the torque converter begins to act as a hydraulic coupling, once the third turbine becomes fully engaged and no multiplication of torque occurs. So at speeds higher than 65 mph, the Turboglide acts as if engaged in top gear, while below that speed, torque multiplication changes imperceptibly. Continuously Variable Transmissions (CVT) offer similar performance characteristics, though with a completely different mechanical principle. History The Turboglide was designed under the supervision of Frank Winchell, Ed Cole and Robert P. Benzinger at Chevrolet engineering. Although it offered remarkable performance and smoothness, the execution of the first 1957 units led to substantial customer complaints and the unit was continuously upgraded to improve its durability until it was discontinued in 1961. The 1959 Turboglide incorporated very significant changes intended to improve its durability, some of which were possible to retrofit to earlier versions. Some enthusiasts reported that Turboglide had better reliability when coupled with the smaller 283 cubic-inch Turbo-Fire V8, than with the big-block 348 Turbo-Thrust engine. The Turboglide was not GM's first attempt at a mass-produced aluminum-case transmission. That was accomplished by the Detroit Transmission Division during development of the Model 315 Dual Coupling Hydra-Matic four speed transmission, which was brought to market for 1956 Cadillac, Oldsmobile and Pontiac models with great success. Chevrolet did not have the benefit of Detroit Division's experience in aluminum case casting, and engineering errors were made, exacerbated by a lack of pre-production testing. As a result, there were many complaints of the aluminum case cracking from the transmission operating pressures. This is why customers of those vehicles called it the "Terribleglide" transmission. GM continued to improve this and other areas of the transmission, but by 1961 the Turboglide was dropped from the GM lineup. Notes References 1958 - 1960 Chevrolet Turboglide Transmission Construction and Operation Automotive transmission technologies Automatic transmission tradenames General Motors transmissions