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The Turbo-Hydramatic Transmission: The Great Equalizer


Bob “Beaver” Butter’s G/S Wackey Wagon was powered by a 270-horse 283 with a 4-speed. The wagon was originally a four-door sedan owned by the adventurist Jeff Zaborowsky and Bill Gracik. (Photo Courtesy Bill Truby)

I don’t know where all those tri-five Chevy sedan deliveries would have been without the Hydramatic; but I’ll tell you one place these quasi cars/trucks wouldn’t have been, and that is in Stock Eliminator. There is no way these hybrids could have dominated the way they did without the benefit of the 4-speed Hydramatic. It may be common knowledge today, but the sedan delivery (based on a passenger car chassis) was never available with the Hydramatic. The loophole that the Chevy racer drove through was the fact the delivery was sold and marketed as a commercial vehicle, and the Hydramatic was listed as an available option in commercial vehicles.

To tell you how wrong the Hydramatic in a sedan delivery was, when racers attempted to install the transmission between the passenger-car frame rails, it was necessary to modify and strengthen the frame mounts. There was no way to bolt-in the transmission to the passenger car frame. The NHRA really did these guys a favor when the rules allowed pre–1961 stockers to run any engine produced by the same manufacturer, as long as the engine was manufactured in the same year. This opened the floodgates, saturating the stock category with dual 4-barrel and fuel-injected 283-powered sedan deliveries.

The Hydramatic was first introduced by General Motors’ Oldsmobile Division in 1940. Weighing close to 250 pounds, the transmission was a bulky piece and not overly efficient. Unlike the later Turbo-Hydramatic 3-speed transmission (Turbo 350, Turbo 400), the 4-speed Hydramatic did not use a torque converter but instead relied on a fluid coupler, which did not multiply torque at stall. The fluid coupler allowed slippage so that the engine idled when in gear. The fluid coupler consisted of two pumps, held together by 33 bolts. The front pump was driven by the flywheel and the rear pump (or turbine) drove the output shaft.

There were two different Hydramatics available: one designated for commercial use, which sported a 4.09:1 first gear, and another for passenger car use (Oldsmobile and Pontiac), which incorporated a 3.86:1 first gear. With that kind of gearing, you can see why the transmission was so popular.

The NHRA finally came to its senses in 1969 and banned the Hydramatic at the end of the season. By that time, companies such as A-1 Transmission on the West Coast and Vitar in the East had discovered how to make the cast-iron Powerglide in these old Chevys live, and had higher-stall converters available.


Chevy Power! 1956 Chevy 210, powered by a 225-horse 265, the Chevy was a regular Division One Cecil County
winner. Norm Phillips drove and wrenched on the Chevy.
(Photo Courtesy Carl Rubrecht)


Don Quartarone took advantage of the NHRA’s allowance of the Hydramatic transmission in the sedan delivery body. The Vitar-prepared Hydramatic helped the 220-horse O/SA 1957 Chevrolet run solid 13.90s during 1969. Don ran the sedan delivery through 1971 and was lucky enough to have Dan Jesel build the 283, which featured M/T slugs, a General Kinetics cam, and Stahl headers. This was the last engine built by Dan before leaving Duffy’s. M&H planted the power from the 4.88:1 gearset. With rule changes in 1970, Don made the switch to a Vitar-prepped Powerglide transmission. (Photo Courtesy Carl Rubrecht)


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