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Chrysler transmissions-Vacamatic semi automatic..

Looking for a used transmission? Try finding the first known production automatic transmission in 1941 built by the Chrysler Corporation? Known in 1941 as the M4 Vacamatic transmission. In reality it was the first semi-automatic transmission which was marketed by a major manufacturer. Chrysler Corporations first attempt to compete against rival’s automatic transmissions.

Being a hybrid of sorts, it still had a clutch, primarily to change range. In normal driving, the clutch is not used. The transmission itself was a fully synchronized manual type, with four forward gears, one reverse; where the shifting was done ‘automatically’ by a vacuum cylinder setup as in the early, M4, or the more advanced technique using hydraulic cylinders in the M6, Presto-Matic. The main difference was the addition of a fluid coupling between engine and clutch, and the shifting mechanism.

Fluid coupling as it was called then, was the first working torque converters. Which, theoretically speaking and mechanically have not changed as much as one might think in over 60 years, except for the currently used ‘lock up’ systems in modern torque converters.

I personally had one for a few years, did not drive it much, as my shop inherited it because the customer never picked up the finished product.

That being said, driving one was/is quite an ordeal compared to putting it in drive and going. Starting on take-off, one would disengage the clutch, then choose a ratio (High for normal driving), and, while being stopped with foot on the brake, engaging the clutch. Pressing the accelerator would move you forward, in third, with the fluid coupling connecting the engine to the transmission. Upon reaching 15-20 mph, I would back off the gas pedal and wait for a ‘clunk’ to occur (the automatic shift), and you would continue in fourth gear. Low range was quite similar, but with a much lower gear ratio, it was used in particular at slower speeds. It is also possible to start in Low, allow the shift, then move the range selector to High, using the clutch, and continue in High.

Not to be mistaken for a performance transmission, it was fine behind the six or eight cylinder flathead engines of the day, but once Chrysler introduced the V8 Hemi engine it was time to design a new series of stronger, modern fully automatic shift transmissions. However, over the years this transmission has acquired a reputation for absolute reliability.

Chrysler trivia. Not much chance of finding a low mileage used transmission here! However, a remanufactured transmission can be purchased from only a small faction of the best transmission suppliers. Which brings me to the term remaufactured, which indicates changing the ‘originality of the transmission, which is not acceptable to collectors. Realistically speaking, for the folks that actually may be interested in acquiring one of these old timers, a transmission rebuilding and supply company would sublet this to a bonifide antique transmission rebuilder.

The other issue in terms of rebuilding used Chrysler transmissions such as this, is that most of the original people who worked on them are dead or forgot how to work on them. I was lucky, when I entered the field in the ’70s, I worked with some ‘oldtimers’, who tought me how to rebuild these transmissions. It was pure luck, because within 5 years we foe all practical purposes stopped seeing these old transmissions due to attrition. Fortunately for me, I have a photographic memory for all mechanical components and still can rebuilt one of these old beasts today.

Yes, a touch of trivia, but what kind of dull blog would we be offering you if we never covered some unusual historical and very cool older transmissions and their history? I’m sure most of you are familiar with the current name Chrysler, Dodge, and Plymouth Enjoy..Called the Torqueflight. Which, most likely is what your interests would be in terms of transmissions..

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