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Fluid Drive is the trademarked name that Chrysler Corporation assigned to a transmission driveline combination offered from 1939 through 1953 in Chryslers, 1940 through 1953 in DeSotos, and from 1941 through 1954 in Dodge models. The fluid drive element was a hydraulic coupling inserted in place of the flywheel, and performed the same function as a modern torque converter, only without torque multiplication. A conventional clutch and three-speed or four-speed manual transmission was installed behind the fluid coupling, although a semi-automatic was optional from 1941 for Chrysler and DeSoto and from 1949 for Dodge.


The fluid coupling and torque converter was invented by the German engineer Foettinger in the early 1900s. For non-marine applications he licensed the development of the fluid coupling to the British engineer Harold Sinclair and his Fluidrive Engineering Co Ltd (now part of Voith AG). Following the development of the fluid coupling, Sinclair in turn licensed the fluid coupling, now also known as ‘Fluidrive Coupling’ to many companies including the Chrysler Corporation. Many automobile historians confuse Chrysler’s Fluid Drive with the Corporation’s so-called semi-automatic M5/M6 transmissions, which were marketed under various names as “Simplimatic” (Chrysler), “Tip-Toe Shift” (DeSoto), and “Gyro-Matic” (Dodge). Unfortunately, Chrysler itself contributed to the confusion by referring to both the standard-shift fluid drive and M6 installations indiscriminately as "Fluid Drive" in much of their marketing and sales literature. General Motors also used a fluid coupling for the full-automatic Hydramatic transmission, introduced for 1940.


The standard Fluid Drive configuration consisted of the fluid coupling and a manual transmission and clutch in tandem. If the Fluid Drive was mated to a manual transmission, the driver still needed to use the clutch to shift between any of the gears. The presence of Fluid Drive, however, prevented the driver stalling when taking off from a dead stop. The driver could also come to a stop in any gear without using the clutch and could then proceed without shifting or using the clutch. Naturally, acceleration from a stop was much slower in high gear than it was in first. It must be emphasized that Fluid Drive was not a transmission, only a fluid coupling between the engine and clutch.

Fluid Drive could also be mated to the semi-automatic transmission, which was not automatic in any way and should not be confused with Fluid Drive. With the semi-automatic transmissions, the driver shifted manually, selecting reverse or a low range and a high range. Each 'range' had two speeds. To shift between them, the driver accelerated then released pressure on the accelerator. In high range, this shift point was about 23 mph (37 kmh). The transmission shifted into high speed range, the driver then depressed the accelerator pedal, and continued accelerating. The solenoids on the transmission connected to the carburetor and ignition system and momentarily interrupted engine operation to allow trouble-free shifting.

The driver could down-shift for passing by fully depressing the accelerator. The clutch was needed to change between low and high range. The fluid drive system allowed the driver to stop at a light or in traffic and remain in gear without depressing the clutch. The driver could, if not concerned with fast acceleration, drive the car all day long in high range, stopping and starting, without ever having to touch the clutch pedal or gearshift lever unless faster acceleration or reversing was required. For this reason, DeSotos and Dodges were favored by city cab companies from the mid Forties to early Fifties.

The semi-automatic came under a variety of names - Vacamatic, Prestomatic, Fluidmatic (Chrysler), Simplimatic, Tip-Toe Hydraulic Shift (DeSoto) and Gyromatic (Dodge).

A Fluid Drive Dodge with Gyromatic was far less expensive than a Hydramatic-equipped Pontiac, and had the effect of making city taxi-driving far easier. In 1950, a Dodge Coronet, which had Fluid Drive standard, offered Gyromatic for $94.60, while Hydramatic was a $158.50 option on Pontiacs.

M4 and M6 transmissions[edit]

Main articles: Vacamatic and Presto-Matic

The fluid drive fluid coupling was also used in conjunction with Chrysler’s M6 Presto-Matic semi-automatic transmissions. The M6 was in reality a two-speed manual transmission with a conventional clutch mounted behind the same fluid coupling unit that was installed in straight Fluid Drive cars.

The M4 Vacamatic had two forward speeds and reverse. There was a manual Pull-Cable to lock out the underdrive in the early models. From 1949-1952, Dodge models with the conventional 3-speed Fluid Drive carried front fender emblems that said “Fluid Drive.” The M6 Models had emblems that proudly proclaimed “Gyromatic.”

In the 1941 brochure for Chrysler automobiles, a silhouette of the car's drivetrain was depicted against an outline of the car body, with the astonishing caption of an arrow pointing to the transmission: "Miracle Happens Here"! The transmission shown was an early variant (M4 "Vacamatic") of the later M6 transmission and was marketed to compete with the new Oldsmobile fully automatic, clutchless Hydramatic transmission, introduced in the fall of 1939 on 1940 Model year Oldsmobiles. The Hydramatic was embraced enthusiastically by consumers, and was installed in 45% of 1941 Model Oldsmobiles.

See also[edit]

External links[edit]


Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Fluid_Drive — Please support Wikipedia.
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120 news items

Boston Herald
Fri, 14 Aug 2015 05:11:15 -0700

Because of the potential damage from slippage when cold, my suggestion is to add half a can of SeaFoam Trans-Tune to the transmission fluid, drive the vehicle for a couple of weeks, then have the transmission professionally serviced — drain, flush ...

Reno Gazette Journal

Reno Gazette Journal
Fri, 07 Aug 2015 13:33:02 -0700

Acceptance was slow, of Hydramatic, Dynaflow, FordoMatic, Fluid Drive and Powerglide – “slush,” we called them, or PNDLR. In fact, the earlier units didn't even have a “park” gear. (In later years we'd pay a premium for four-on-the-floor over slush. Go ...
Minneapolis Star Tribune
Fri, 24 Oct 2014 05:11:15 -0700

But I would suggest the KISS approach — add a half-can of SeaFoam Trans-Tune to the transmission fluid, drive the car for several weeks, then have the transmission fluid and filter changed. Q: I have a 2009 Chevy Malibu with the four-cylinder engine ...

Knoxville News Sentinel

Knoxville News Sentinel
Wed, 20 May 2015 05:07:47 -0700

The closest I came to being sent to a hot spot was when the major in charge of USAREUR's public information division said I was on alert for Operation Fluid Drive, an evacuation of Americans from Lebanon during one of the Middle East's periodic ...

Ward's Auto

Ward's Auto
Wed, 29 Jul 2015 07:30:35 -0700

Reporting on changes in the upcoming '41 models, WAR tells readers to look for more widespread availability of the Fluid-Drive transmission at Chrysler, where some models may offer it at no added cost. The newsletter also says it expects electrically ...


Wed, 10 Jun 2015 00:18:54 -0700

Benjamin Krause LA Times just released a report about female veterans' suicide rates — female veterans commit suicide at a staggering six times the rate of civilian women. And what is our government doing about it? A back injury forced female veteran ...

Boise State Public Radio

Boise State Public Radio
Tue, 12 May 2015 20:56:15 -0700

According to data from the U.S. Fish and Wildlife Service, women are the fastest growing group of hunters in the country. While the number of young men picking up the sport has taken a nose dive in the last 30 years, participation by young women has ...

Boise State Public Radio

Boise State Public Radio
Mon, 22 Jun 2015 09:07:30 -0700

skip to main content. Boise State Public Radio logo. KBSX News 91.5 FM | KBSU Classical 90.3 FM. Site Menu DONATE. Listen Live. News. BBC World Service · Classical. Fluid Drive · Jazz. Menu. Home · News ...

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