Secrets of the Chevy Powerglide 1950-73

The Powerglide automatic transmission loyally served Chevrolet and General Motors for nearly a quarter of a century.   
When the Chevrolet Powerglide made its debut in 1950, it was the first automatic transmission intended specifically for the low-priced field. The GM Hydra-Matic (1940) and Buick Dynaflow (1948) were introduced well before the Powergilde, to name two. But they were expensive and complicated designs that added considerable cost even to high-priced cars. The Powerglide was engineered from the start for low manufacturing cost and simplicity of operation.
The Powerglide has also been described as a “poor man’s Dynaflow,” and there’s more truth to that throwaway line than there might seem. While the two transmissions are quite different in detail—and in cost—both the Buick Dynaflow and the Chevy Powerglide were developed by automatic transmission guru O.K. Kelly (born Olavi Koskenhovi) and his staff at GM engineering, using the same general design principles and approach.

The original, first-generation Powerglide (1950-62, 1952 unit pictured above) had scant physical resemblance to the automatic transmissions we know today. There was no sump or pan on the bottom, and instead of a one-piece aluminum case, the Powerglide used a collection of cast-iron housings that bolted together. As a result, the unit was quite heavy at better than 240 lbs, and there were a number of gasketed joints with the potential for fluid leaks.

The heart of the first-generation Powerglide was its torque converter (above). In fact, the earliest Chevrolet technical literature often referred to the unit as a “torque converter transmission” rather than the more simple and familiar “automatic.” The original 1950 design employed a five-element, bolt-together converter that provided a torque multiplication factor of 2.20:1. Later, a simplified three-element converter was developed.
A two-speed planetary gearset with a first-gear ratio of 1.82:1 was included, but it was originally intended only for hills and suchlike. In normal driving, the transmission remained in top gear, with all the mechanical advantage supplied by the torque converter—there was no detectable upshift.  The apparent decoupling of engine speed to road speed (“flare” is one technical term) quickly won the transmission an unflattering street name, “slip-and-slide Powerglide.” (In a similar way, the Dynaflow became known as the “Dynaslush.”)

​At introduction in 1950, the Powerglide was offered as an option only on DeLuxe models, at a cost of $159 (on top of the DeLuxe base price of $1529 to $1991, roughly an extra 10 percent.) A chrome badge on the deck lid proudly proclaimed “POWER GLIDE,” and to compensate for the lack of torque multiplication, Powerglide cars got a slightly larger six-cylinder engine (235 vs. 216.5 cubic inches) with hydraulic valve lifters and 105 hp rather than the standard 90 hp. Meanwhile, the rear axle ratio was reduced from 4.11:1 to 3.55:1 to manage driveline noise and harshness.
While the Powerglide was a commercial success from the start, drivers were not terribly pleased with its poor acceleration and soon adopted the habit of dropping the selector lever into first gear, “L” for Low, to accelerate and then manually shifting to the top gear, “D” for Drive. (The shift pattern was PNDLR, eventually revised to the familiar PRNDL.) Fearing the damage and wear that could result from this practice, GM engineers in 1953 provided an automated first-gear start and programmed upshift at up to 42 mph depending on load, and a throttle-controlled kick-down function as well.
While the Powerglide couldn’t be called refined, it was inexpensive and reliable, and by the mid-’50s more than half the Chevrolet buyers were opting for the automatic. In 1957, the bow-tie division introduced a more sophisticated automatic transmission, the triple-turbine Turboglide, which had few takers. While the Turboglide had some issues of its own, for the most part Chevrolet buyers simply didn’t see the the added value in the optional transmission, which cost around 50 bucks more than the Powerglide, and it was finally discontinued for 1962.

Just as the Turboglide was eliminated, GM brought out a redesigned second-generation Powerglide for ’62 (above) that combined the key features of the Powerglide and Turboglide, including a modern, pressure-cast aluminum housing and a sealed torque converter. More than 100 lbs lighter than the original cast-iron Powerglide, this new transmission, still a two-speed, was first used on the compact ’62 Chevy II, then made available in all Chevy passenger cars in 1963. Variants of the Powerglide were also used in the Corvair and Pontiac Tempest transaxles, and one of the final applications was in the subcompact 1971 Chevrolet Vega.
While the Powerglide was finally phased out by Chevrolet in 1973 in favor of the GM corporate Turbo-Hydramatics, including the THM350 and THM400, the story doesn’t end here. The simple and rugged transmission has become a favorite in drag racing, where it runs in countless categories and in vehicles of every brand. Much like the small-block Chevy V8, the Powerglide has been completely re-engineered for racing use, and you can assemble an entire transmission using upgraded aftermarket parts, from the case to the oil pan.
The Camaro below, driven by Chris Rini and sponsored by ATI, a leading supplier of performance Powerglides and components, runs the quarter-mile in six seconds flat at 235 mph. Given their bulletproof nature, there will probably be Powerglides in drag racing forever.  –Photo below courtesy of ATI Performance Products.

Article courtesy of Mac's Motor City Garage.