The Chrysler-Plymouth-Dodge-DeSoto Hy-Drive automatic transmission

Hy-Drive semi-automatic transmissionThe Hy-Drive transmission that became available (in Plymouths, at least) in April, 1953. It was a manual gear box mounted behind a torque converter. Advertised as the transmission for those who wanted the ease of automatic driving yet the ability to select their own gears, it really was just a stop-gap measure to mark time until the new fully automatic Powerflite would become available during the 1954 model year.

Basically, the Hy-Drive was Chrysler's old Fluid Drive refined so that there was no need to lift the accelerator to shift gears. The clutch pedal - in red rubber - was necessary only for putting the car in gear.

The transmission shared the engine oil, necessitating a full ten quart oil change. Fortunately, the recommended mileage between oil changes was doubled.

Since the buying public was clamoring for automatic transmissions, Plymouth tried to make the "Hy-Drive" look as "automatic" as possible by placing an indicator quadrant on the steering column, even though the lever still shifted in the normal H-pattern. The one additional advantage of the Hy-Drive was its price. At $145.80, it was much cheaper than any fully automatic unit.

Although highly touted in 1953, the Hy-Drive was seldom mentioned in 1954 once the new Powerflite automatic became available.

This section contributed by Curtis Redgap. Click here to read more of his articles.

The Hy-Drive so called semi-automatic transmission was a very late 1953 model year introduction and carried over intact to 1954. My Father [who owned a dealership] hated it. There was no way for a dealer to convert a standard model to the "Hy-Drive" option because essentially under the sheet metal, it was a totally different car! The engine block was completely different, the transmission required substantial changes to the body in the cowl area. The clutch was totally different with substantial changes to the linkage that engaged it. The drive line was not as long, and used a longer, heavier tail shaft to handle the additional torque. The gear ratios were also different. The speedometer cable was much longer. The radiator was larger to handle the extra heat from the transmission. The carburetor used a dashpot to keep from stalling when quick lifts off the accelerator were made. As well the front floor pans were different to handle the increased clearance for the transmission.

For whatever reason Chrysler engineers chose to share the engine oil with the transmission! 11 quarts were required when the filter was changed! Granted the intervals were once every six months, but still it was a bother and required that the transmission and engine be drained separately, although you filled the whole thing through the engine filler tube.

Yet, 75,000 Plymouths got that transmission. [Which is a note to anyone that might find a 1954 with Hy-Drive and seek to restore it. Not much will mix in the driveline with a non Hy-Drive model. As well, the body is different underneath around the pans and cowl area. Better to find the Powerflite model, which required no such extensive fixes to fit.] Even with its late model year introduction of the Powerflite to the Plymouth, 61,000 units were equipped with it.

Mike Sealey added: Outside the US, export Dodges and DeSotos based on US Plymouths also used Hy-Drive, which could cause some confusion. A suspect car would generally have a Plymouth dashboard.

Argent wrote:

I heard a couple of accounts that Chrysler could've developed a fully automatic transmission earlier, but K.T. Keller didn't want to, thinking it unnecessary. A mistake...Pontiac didn't really want the Hydra-Matic, either, when they introduced it for 1948, but within two years 80% of their U.S. sales had it. FordMoCo was so desperate for an automatic for Lincoln (the BW-built Ford-O-Matic didn't have the capacity for the big Lincoln engines) that they ended up buying Hydra-Matics until '54. So did Kaiser, Frazer, Nash, Hudson, and Rolls-Royce.

Hemi Andersen wrote:

The driver did all the shifting with "Hy-Drive" exactly the same way the driver shifted a 1948 Dodge with Fluid Drive.

"Hy-Drive" meant you could start off in high (3rd) gear. It was quicker than fluid drive, but not by much.

Powerflite transmission. | Fluid Drive transmission

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