General Motors (GM) Powerglide transmission sequence was P-N-D-L-R until 1957. It changed in 1958 to a P-R-N-D-L sequence. The earlier GM sequence was criticized by auto safety experts for positioning reverse after the forward gear. Instead, it redesigned the sequence to place reversebetween park and neutral.
Powerglides were introduced into the Chevrolet models as shiftless automatic transmissions. Some models of Oldsmobile and Pontiac's by GM used a Hydramatic design that was discontinued in 1953 according to Hemmings.
Concern with the Powerglide sequence was that a driver could miss low and shift into reverse by mistake even though it was necessary to lift up on the shift to change gears.
Earlier versions had detents, a catch in a machine that prevents motion until released,at the "park" and "reverse" positions. In subsequent versions a third detent for the "neutral" was added.
In 1962 another variation of the Powerglide sequence was introduced and became the standard. It was the opposite of the earlier versions, from front to back, P-R-N-D-L.
GM made the non-shift cast-iron Powerglide transmissions up to 1962. The word, Powerglide, is stamped transmission body. Powerglide transmissions were phased out after 1964 in favor of a new model of two-speed Super Turbine 300 and three-speed Turbo-Hydramatics.