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The Super Turbine 300 (abbreviated ST-300) was a two-speed automatic transmission built by General Motors. It was used in various Buick, Oldsmobile, and Pontiac models from 1964-1969. It was the same transmission marketed under different brand names by each division including ST-300 by Buick, Jetaway by Olds and simply Automatic by Pontiac.
The ST300 had a three-element torque converter, a front and rear multiple-disc clutch pack, and a compound planetary gearset with a front band and a clutch pack for reverse and manual low gear. The unit was either air cooled or cooled with a small auxiliary oil cooler located beneath the engine radiator. It had a die cast aluminum case, and weighed 152 lb (69 kg).
It was programmed to start in low gear, providing a gear ratio of 1.765:1 plus the additional low-speed multiplication of the torque converter. The shift pattern was Park-Reverse-Neutral-Drive-Low. In Drive at full throttle, it would upshift from low gear to high gear at 60-65 mph (97-105 km/h).
From 1964-1967, Buick and Oldsmobile versions of this transmission used a torque converter with a variable-pitch stator called Switch-Pitch by Buick and Variable Vane by Olds. The stator blades moved from high to low position by an electrical solenoid and a stator valve, controlled by a switch on the throttle linkage. At light to medium throttle, the stator blades were at 32°, providing a torque multiplication of 1.8:1 and a converter stall speed of approximately 1800 rpm. At 2/3 to full throttle, the blades switched to the 51° high position, giving torque multiplication of 2.45:1 and a stall speed of approximately 2300 rpm. The blades were also set to the high position at idle to limit creep when stopped in Drive. The variable-pitch stator was eliminated after 1967. This feature was not used on the Pontiac versions of this transmission.
The Super Turbine 300 (Jetaway) was introduced for the 1964 model year as a replacement for the earlier Buick Dynaflow and Oldsmobile/Pontiac Roto Hydramatic transmissions. It was the only automatic offered on GM A platform cars (Buick Skylark, Oldsmobile Cutlass, and Pontiac Tempest) through 1966, and was available on the full-sized Buick LeSabre and Oldsmobile Jetstar 88/Delmont 88 as a less expensive alternative to the three-speed Turbo-Hydramatic. If it was used with a V8 motor, the transmission had liquid lines which is cooled by the radiator whereas those coupled to the Chevrolet-sourced inline six was air cooled.
From 1967-1969, the Super Turbine 300 was also available on the sporty Pontiac Firebird with the overhead cam in-line six-cylinder (230 and 250 cubic inches) or small V8 engines (326 and 350 cubic inches).
The Super Turbine 300 was discontinued entirely after the 1969 model year in favor of the TH400 and lighter TH350 Turbo-Hydramatic, the latter using the Super Turbine 300's tailhousing.
Super Turbine 300s were the first GM automatics to incorporate multi-case bellhousings (ST300s were bolted behind BOP powerplants along with the Chevrolet inline six) -- which were later used with its successors -- the THM350 and THM2004R overdrive.
Due to its two-speed with torque converter design, the Super Turbine 300 is often confused with Chevrolet's Powerglide -- which was also a two-speed torque converter transmission, but the ST 300 was of a completely different design and shared no parts with the Chevy unit, which had been around since 1950.
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