I'm not sure what you want to know. GM held on to 2-speed automatic transmissions like the Powerglide way too long. It was well past its use-by date by the 1970s yet GM persisted with it through 1973, even installing the Powerglide in the Vega.

Performance of Powerglide-equipped cars was hampered by lack of an intermediate/passing gear, especially models with small 4 and 6 cylinder engines. The Powerglide is simple and rugged though, and relatively simple to overhaul when needed. For that reason it is still favored by drag racers.

The original Powerglide of 1950 did not shift automatically between 1st and 2nd gears. Like the Buick Dynaflow it was intended that normal driving would be done in top gear with all mechanical advantage provided by the torque converter. Automatic shifting was added for 1952. A semi-automatic version called "Torque-Drive" returned in the late 1960s, requiring manual selection of gears.