By 1953, Chrysler was starting to pay the price for not having a real automatic transmission. The two-speed PowerFlite became available for senior models late in the ’53 model year, but until the spring of 1954, Plymouth had to make due with the offensively rudimentary Hy-Drive transmission, which married a torque converter to a conventional three-speed manual gearbox. Let’s take a look at how it worked, and why Plymouth offered it in the first place.
Even before its demise in 1999, Plymouth was one of those brands that invite the same kind of inexplicably fierce loyalty as underdog sports teams. You can scarcely mention it without some ultra-fan voicing their conspiracy theories about how it was unfairly dragged down by sinister forces (at Dodge Division, typically), or expounding on the one weird trick they’re sure would have made Plymouth No. 1 in the world. They’ll insist, like Marlon Brando in On the Waterfront, that it coulda been a contenda.
Yet, when I looked again at the workings of the 1953–1954 Plymouth Hy-Drive, I was overwhelmed not by admiration for a plucky underdog, but rather by a sense of mounting outrage at this ramshackle transmission and the palpable contempt it evinced for Plymouth customers.
Chrysler had ample engineering talent in this era, but they waited until almost every domestic rival had an automatic transmission before coming up with anything for Plymouth — their biggest-volume brand — and then they finally did, it was this crude, overpriced kludge. It makes me kind of mad, in the same way the early Vega and Citation make me mad at Chevrolet and GM for their obvious disdain for customers without the money to buy some more profitable model.
From the late ’30s into the early ’50s, Chrysler had wasted an immense amount of time and resources on their unloved semi-automatic transmission (whose various iterations are too numerous to even summarize here). This used a fluid coupling (and later a torque converter), but it wasn’t truly automatic, and it still required some use of the cynically described “Safety Clutch” — a concept American buyers had pretty resoundingly rejected well before World War 2.
Finally, after much dithering, Chrysler grudgingly came up with the two-speed PowerFlite, which was sturdy and competent, if hardly class-leading even for 1953.
PowerFlite would eventually be available for Plymouth, but Chrysler had waited so long that it took them some time to get production rolling. When PowerFlite first appeared in regular production in June 1953, it was only made at one plant, which was only able to turn out around 35,000 transmissions before the end of the year, most of them earmarked for the senior Chrysler and Imperial lines. (PowerFlite also became optional for DeSoto and Dodge for 1954.)
However, Plymouth had to have something. Rival Chevrolet had introduced its early Powerglide in 1950, while Ford and Studebaker had added fully automatic transmissions by 1951. Not all buyers of that period ordered automatic transmissions, especially in the low-price field, but it was increasingly common: By the 1952 model year, over half of ALL new domestic cars were ordered with automatic, and not having one was becoming a real problem. I assume dealers were screaming for relief.
Hence, Hy-Drive, which became available in March 1953 for the princely sum of $145.80 — a relative worth of over $2,600 in 2025 dollars.
In a broad sense, Hy-Drive was absurdly simple: It was really just a heavy-duty version of the usual Plymouth “Synchro-Silent” three-speed manual transmission, synchronized on second and third, with a hydraulic torque converter interposed between the engine crankshaft and the heavy-duty friction plate clutch. This made it physically larger than a standard transmission, since the addition of the torque converter meant the housing had to be enlarged to make room for the plate clutch, and the gearbox had to sit farther back.
Hy-Drive didn’t have its own oil pump, so it used engine oil to charge the torque converter. Engines for Hy-Drive cars got special oil passages to direct oil from the main gallery to the transmission, plus a replaceable bypass-type oil filter. Oil capacity was doubled (from 5 quarts to 10); Plymouth recommended twice-yearly changes, more often in severe use. The carburetor on Hy-Drive cars also got a spring-loaded dashpot to keep the engine from stalling on an abrupt drop to idle speed, and there was an electrical switch that disabled the starter circuit unless the transmission was in neutral.
Hy-Drive transmissions used the same 11.75-inch, four-element torque converter that would be fitted to 1954 Dodge PowerFlite cars. The impeller was bolted to the engine crankshaft through a flange, so the converter always rotated at engine speed. There were two stators between the impeller and the turbine, each with its own one-way clutch to allow them to provide leverage for torque multiplication.
The turbine drove the input shaft of the plate clutch, which was operated by a foot pedal in the normal manner. This was a special high-pressure clutch, 8.5 inches in diameter, with none of the usual torsion springs. A low-friction clutch linkage provided additional leverage to keep clutch pedal effort within reason.
Behind the plate clutch was the gearbox, which worked just like a regular three-speed manual transmission, but had closer-ratio gears: 2.37 in 1st, 1.68 in 2nd, 1.00 in 3rd. Its gears and drive pinion were also beefed up to increase their torque capacity. As with the heavy-duty clutch, this was necessary because the gearbox was “downstream” of the torque converter and had to absorb the additional torque multiplication provided by the converter, which could be up to 2.6 times engine torque.
The reason Chrysler called this transmission “Hy-Drive” was that you could theoretically put the gearbox in its direct 3rd gear (after starting in neutral) and then leave it there, relying on the torque converter as a continuously variable transmission. Chrysler pointed out that the converter stall ratio (2.6 to 1 at about 1,300 rpm) was about the same as first gear in the normal Plymouth three-speed stick shift (2.57 to 1). This dropped off progressively as output speed increased, and once the output shaft was turning about 85 percent or more of engine speed, the ratio was about 1 to 1.
Using Hy-Drive in that way condemned you to the slow lane. Wilbur Shaw, testing a 1953 Plymouth with Hy-Drive for Popular Science, needed more than 20 seconds to reach 60 mph, and Motor Life‘s 1954 Plymouth Belvedere needed a yawning 24.5 seconds. The standard 217.8 cu. in. (3,569 cc) Plymouth flathead six had 100 gross horsepower to move about 3,500 lb of car, and the torque converter alone just wasn’t enough for more than very leisurely acceleration.
Going through the gears provided much better performance — Shaw got to 60 mph in about 16 seconds that way, which wasn’t bad for 1953 — but that required manual shifting.
Of course, owners of automatic Buicks, Packards, and 1950–1952 Chevrolets were used to having to manually select Low for better getaway, but Dynaflow, Ultramatic, and Powerglide had planetary gears, so all a driver had to do was move the lever, with no clutch pedal to worry about. With Hy-Drive, shifting through the gears required manually de-clutching and matching revs, just like a conventional manual transmission.
All this might have been more acceptable if Hy-Drive were at least cheap, but at about $146, it cost only $32 less than Chevrolet charged for Powerglide, which was actually automatic and didn’t need a clutch pedal. Ford-O-Matic and Studebaker Automatic Drive were still more expensive, but they gave you three forward speeds, with the option of starting in 2nd with fully automatic shifts or starting in 1st for better acceleration — again with no manual clutch. Ironically, the main reason Hy-Drive was so expensive was probably because it was such a kludge: Because it required modifications to the engine block (to connect its oil passages to the torque converter oil circuit) and the floor pan (to accommodate the larger case), it wasn’t interchangeable with conventional transmissions, and was more expensive to build.
If you drove mostly in heavy city traffic, the added convenience of the Hy-Drive torque converter might have been attractive: You could crawl along on converter creep, seldom touching the clutch, with no fear of stalling the engine. However, in lighter traffic, you had to put up with sluggish performance unless you were willing to shift for yourself, and because there was no way to lock out the torque converter, you were paying a penalty in fuel economy either way.
Many Plymouth buyers were probably better off with the $97.55 overdrive, which gave better gas mileage and included a higher numerical axle ratio (4.10 rather than 3.73) for better acceleration.
Total Hy-Drive production is a little hazy. The Standard Catalog of Chrysler 1914–2000 claims that by July 1953, one in four Plymouths had Hy-Drive. Doing some back-of-the-envelope math based on Plymouth monthly production figures, that might have amounted to anywhere between 60,000 and 95,000 units, perhaps 10 to 15 percent of total 1953 calendar year production. For 1954, Hy-Drive production totaled 75,000 units, about 17 percent of model-year production. Once PowerFlite became available (in late February 1954), interest dried up, and Hy-Drive was gone before the start of the 1955 model year.
I know there’s no car so dorky and inept that it doesn’t have its stalwart defenders, but I can’t summon up much affection for these Plymouths: They’re dumpy-looking; their performance was only adequate; their handling was tipsy even by the standards of the time; their steering was excessively light with or without power steering (which wasn’t offered until 1954); and even the model names were often unappealing. (With all apologies to residents of the English and Canadian towns, “Cranbrook” is just not a mellifluous name for a car, and “Belvedere” mostly reminds me of the Mr. Belvedere movies starring the misanthropic Clifton Webb, whom I cordially detest.)
It’s not that I can’t see what Chrysler was thinking, and in the lexicon of odd and misguided automotive automatic transmissions, Hy-Drive was hardly the worst, but it was the answer to a question no one was asking. Worse, it was an unwelcome reminder to Plymouth buyers that despite accounting for about half of all Chrysler Corporation sales, they were the corporation’s lowest priority — never a good message to send.
Today, like many oddball engineering features on older cars, a Plymouth survivor with Hy-Drive is a moderately amusing novelty. Back then, it bordered on a deadly sin. Chrysler could — and should — have done a lot better.
Related Reading
Curbside Classic: 1953 Plymouth Cranbrook – What The Hell Else Can You Do With A ’53 Plymouth? (by Jason Shafer)
Curbside Classic Capsule: 1953 Plymouth Cambridge Club Sedan – Flaming Flathead Six (by Paul N)
Curbside Classic: 1954 Plymouth Savoy – Unexpected Affection (by Brendan Saur)
I remembered the factoid that Hy Drive shared an oil supply with the engine, making oil changes an expensive proposition, but I recalled almost nothing else about it. Thanks for this.
BMC, sorry, British Leyland make the same mistake with their automatic-transmission-inside-the-oil-pan that put the Austin America into the Curbside Classic Hall of Shame…
Seriously what was wrong with the leadership at Chrysler after WW2? How could they have simply refused to recognize the obvious market for automatics which existed even before the war?
Did Chrysler do no market research? How could the leadership of the company not see the absolute need for an automatic? Was the company’s aging leadership that out if touch with basic reality?
Plymouth’s tardy availability of a true automatic is a head-scratcher. For the money they spent engineering the still clutch-laden Hy-Drive they could have purchased a real automatic from a third party like Borg-Warner, or even GM which sold their automatics to other manufacturers (so did Packard but those would have been too expensive for a Plymouth). A substantial percentage of American car buyers wanted real autoboxes on even low-price cars by ’53-54.
Well, as one might expect, the lag of developing a decent automatic for the Plymouth division would lay directly at the feet of Chrysler leadership, and that means K.T. Keller. Personally appointed by Walter Chrysler as his successor, the guy worked wonders at Chrysler before and during WW2, but was slipping by his retirement as Chrysler president in 1950 (although he remained board chairman until 1956), with what seemed to be an emphasis on government contracts while letting development of civilian products fall to the wayside. Keller went the route of solid, well-built, but stodgy products.
His replacement, Tex Colbert, lacked the same engineering background as Keller and that, more than anything else, is likely why engineering still lagged. IOW, the Hy-Drive was ‘good enough’ for typical Plymouth customers. As it turned out, it really wasn’t, particularly given the hefty price tag for the option versus other, better automatics from competitors.
Of course, Colbert’s focus on styling with Virgil Exner had its own dramatic ups and downs, but that’s another story.
Indeed, how Plymouth would have fared if the Powerflite, Torqueflite and/or an OHV 6 have arrived a couple of years earlier to replace the flathead 6?
We had a 1954 Plymouth, I do not remember the model, 4 dr sedan with Hy-Drive. It had the larger 230 ci flathead 6 and while it wasn’t a snappy performer it wasn’t a slug if dad used 2 then 3 driving it. One evening after our BSA troop meeting, a bunch of us were getting my dad to try a first gear start and see if it could spin one or both rear tires. End result, broke thr left rear leaf spring with a loud bang.
My first foray into hot rodding (I was 14 or 15) I had scored a Carter Ball and Ball one barrel from a Chrysler straight 8, along with the Sisson exhaust manifold mounted choke. The 1954 exhaust manifold still had the mounting holes and I had grabbed the air filter brace from the Chrysler. I bought a kit and cleaned up the carburetor. With dad’s permission I installed it on the Plymouth, BIG difference, that 230ci flathead came alive with that big one barrel!
This primitive arrangement wasnt offered here for local assembly, in fact nobody offered auto trans it was special order only on anything which meant importing a built up car which attracted higher import tariff.
The old Plymouth Cranbrook was built with mods until 63 in Aussie and those came in too a fleet of ambulances were built on them in the mid 50s.
Time to bring a flashback with this article about the 1953-54 Plymouth body morphed into the Aussie Chrysler Royal Down Under.
https://www.curbsideclassic.com/curbside-classics-australian-brands/curbside-classic-1958-9-chrysler-ap2-plainsman-happy-accident/
After Hi-Drive, Chrysler introduced another engineering nightmare when they went to their push-button transmission. They finally came to their senses in 1965 when the push-buttons were eliminated.
Was there a problem with push-buttons?
They were different, when different was costing the company sales.
That convertible is calling out to me! Can’t think too many of those were made.
Once again, Aaron has taught me something new. I had no idea contraption even existed. Surely the capital spent to create the Hy Drive was thrown a rabbit home and would have been much better spend on real, self-shifting automatic.
I drove my dad’s 1949 Chrysler a lot. It had fluid drive and in the city, all you had to do was level the car in second gear. The long stroke six made for smooth takeoffs, with no issues of keeping up to traffic at all. It was simple and effective system.
Thank you for this complete and well-written piece. Given the nature of most automatic transmissions at the time, I assumed HyDrive was lacking, but it’s worse than that. Using engine oil (10 quarts!) is astonishing, as are adaptations like reworking the engine block and floor. It’s hard to imagine a worthy successor to the rather pointless Fluid Drive, but Chrysler found a way.
Yes, it couldn’t have been fun as a salesman for the various Chrysler Corp. marques when the question of an automatic transmission came up on the sales floor in the 1950-1954 time frame…………….
I think that was what that “indicator” was for- so people could see it through the driver’s side window at the dealer and go, “Oh, look! It’s got an automatic!”
The very early ’53 Chrysler Powerflite had an unusual shift quadrant that was evidently changed during the introductory model year.
Even at introduction, Powerflite was a rugged and reliable transmission. It didn’t seem to have a lot of teething issues. It was fully competitive with Chevy Powerglide or the Borg Warner/Fordomatics. When it was designed and well before actual introduction, Chrysler surely must have realized Plymouth needed a true automatic to stay competitive with Ford and Chevy.
Given that need, I’m at a loss to understand why initial Powerflite production capacity was so limited. Hydrive equipped Plymouths required extensive modifications from those with a stick. That project took engineering and tooling resources. I wonder if those resources required for the Hydrive project couldn’t have been more productively employed focusing on a larger scale rollout of Powerflite. I’m sure there are reasons, but they are likely lost to time.
As others have noted, purchased transmission capacity for units like Hydramatic, Ultramatic or Borg Warner may not have been a good match for the Plymouth. However, they may have been a practical match for the larger Chrysler products.
I think Chrysler should have purchased available transmissions for their senior cars and devoted 100% of Powerflite capacity to the Plymouth right from the start. Powerflite capacity may not have satisfied initial demand for automatic shift Plymouths, but at least the possibility could have gotten buyers into the showroom. Of course, they didn’t ask me. I find it easy to solve problems with the benefit of hindsight and a lack of knowledge about what Chrysler may have been up against getting the Powerflite into production.
My first car was a ’53 Plymouth with a standard tranny. I paid $65 for it in 1962, drove it for 3 years and 30,000 miles (repairs only consisted of a new master brake cylinder and a cheap set of new tires) and sold it for $35. A perfect car for a college student!
My family’s second car after a gifted 1941 Chrysler New Yorker was a 1954 Plymouth Savoy HyDrive bought in late 1954. Dad was a Chevy guy but the Plymouth was cheap, being a retired Portland. OR taxicab.. It lasted us three years until it was traded on a 1957 Chevrolet “210” wagon with a Six and Powerglide, a car that has (with help) put me off GM ever since.
Mom thought the Plymouth easy to drive and usually held it in high gear. In hilly San Francisco the torque converter was apparently sufficient with the help of avoiding the steepest hills.
One of the many mementos from my family’s dealership I came across as a kid was that Master Tech bulletin on Hy-Drive, which made no sense to me at the time, and I can see why.
If Chrysler bought Packard after WWII, they could have had Ultramatic by ’51…
The VW Autostick is pretty much the same thing as Hy-Drive, but with the friction clutch function handled electrically. I’ve driven an Autostick and it wasn’t awful and downright pleasant in heavy traffic.
I caught 2 of these 1953-54 Plymouths within a few weeks of each other in late 2020. The white ’53 Cranbrook was awaiting service near my house, and the green ’54 Savoy was offered for sale in Sperryville, Virginia.
Yes, they were homely cars, but I understand they were quite space-efficient, relatively economical, and long-lived.
Very interesting. I don’t know much about all the various Fluid-Drive derivitaves (what’s a Gyro-Matic?). Hy-Drive was clearly the most advanced, but as you pointed out why the Chrysler spend money on a technical dead-end when the replacement (Powerflite) was so close to introduction?
Hy-Drive wasn’t related to the many Fluid Drive derivatives, which did have some ability to change gears by themselves. Hy-Drive was just a three-speed stick shift with a torque converter, so it was much, much less advanced than the Fluid-Torque Drive offered in the senior cars. Fluid-Torque Drive (which Dodge called Gyro-Matic) had a torque converter and four speeds, divided into two ranges, and it could shift automatically between the gears in its current range, although you had to de-clutch manually to shift between ranges.
Thanks once more Aaron. Another great read.
I would say that my grandparents were fortunate to have waited partway through the 1954 model year because their Plymouth sedan was equipped with Power-Flite. Great article! My uncle and aunt both a 1953 with Hy-Drive, which they liked.
My Grandfather bought a ’51 Chrysler Windsor with the semi-automatic, it was his first (and only) car, I think he used it to help stock his mom/pop grocery store; there were some things he couldn’t get delivered. It was the car my Mother learned to drive on (I suspect she might have actually taught my Grandfather after she took driving lessons), though she’s never been comfortable with anything but a full automatic…she stopped driving 5 years ago, but my Dad’s first car was a new ’56 Plymouth Plaza…he hadn’t yet met my Mother, which explains why it had a manual 3 speed and no options (well, maybe a heater but no radio). Dad drove it out to Los Angeles from Massachusetts when he got a job with Hoffman Electronics. They traded it on a new ’61 Rambler Classic Wagon they bought in Compton…it was a 6, but with automatic and radio. My Mom, Sister and I flew out on a prop plane but drove back in the Rambler after Dad got his next job in Pittsburgh (he changed jobs frequently back then, but did the same work, just for different companies).
I had heard that Power Flite also shared engine oil with the transmission, I think that stopped when TorqueFlite had separate fluid for the transmission.
PowerFlite did not share engine oil. Some (not all) of the earlier semiautomatic transmissions used engine oil for the torque converter, like Hy-Drive did, but PowerFlite had its own oil supply for both transmission and converter.