The Chrysler-Plymouth-Dodge-DeSoto Fluid Drive
by Sam Chase
Chrysler's first fluid drive cars were introduced in 1939. They were equipped with a standard 3-speed manual transmission and clutch, but had a fluid coupling in place of the conventional flywheel. This set-up was available on all Chrysler models from 1940 through 1948, and on DeSoto and Dodge models from 1941 through 1946, at a slight extra cost. From 1947 through 1952, the fluid coupling/3-speed manual transmission combination was standard equipment on all Dodge models and optional on DeSotos. In 1953-54, Plymouth offered a variant called "HyDrive", which is a 3-speed manual unit and clutch, with the fluid coupling updated to a modern torque converter (pictured above right).
These cars do not change gears "automatically," but can be held stationary in any gear without disengaging the clutch. They can also be started in any gear without slipping the clutch, although 3rd gear starts are painfully slow. Fluid drive advantages are:
There are also disadvantages:
In 1941, Chrysler offered its "semi-automatic" transmission in combination with the fluid coupling, at considerable (for the time, anyway) extra cost, usually between $100-140 depending on the model on which it was installed. This semi-automatic transmission consists of the fluid coupling, a two-speed manual transmission with integral underdrive, and conventional clutch. The early models (M-4) operate on engine vacuum ("vacamatic"), while the later models (M-5 and M-6) operate on a combination of electric circuitry and hydraulics.
The shift lever is mounted on the steering column, and there is no "shift quadrant" indicating the "gear" the transmission is in, except in later models (1951-53 Chryslers, 1953-1954 DeSotos and Dodges). There are two forward "ranges," low and high, as well as a reverse gear. The shift pattern is the standard "H" minus 1st gear, as per the illustration on the right from the 1946 Chrysler Owner's Manual.
There are four forward gear ratios:
To start the car under normal conditions (relatively flat road, light load), the driver depresses the clutch pedal and shifts into High range. At this point, the transmission is in "Underdrive High" which means that the transmission is in Direct Drive with the underdrive gearing engaged. When a speed of approximately 14 MPH is attained, the driver lifts his foot completely off the accelerator pedal, the underdrive gearing disengages, and the car is now in Direct Drive. If extra pulling power or acceleration is desired from a dead stop or the car is starting from rest on a steep hill, the driver shifts into Low range where the transmission is in Underdrive Low with the underdrive gearing engaged. When the car reaches approximately 6 MPH, the driver lifts his foot off the accelerator, the underdrive disengages, and the car is in Low. At this point a manual shift from Low range to High range (driver steps on clutch pedal and moves shift lever from the "low" to "high" position) brings the car into Direct Drive.
The advantages of this transmission vs. a conventional manual or fully automatic "clutchless" transmission are:
Disadvantages:
Chrysler indiscriminately referred to both the standard and semi-automatic fluid-coupling transmissions as "Fluid Drive" in its promotional and technical literature. This contributed greatly to the confusion between the two types, and many Chrysler Corp. car owners of that time did not understand the difference. Many who had the fluid drive/3-speed manual configuration were not aware of any difference between that and the conventional flywheel set-up.
The fluid drive and semi-automatic transmissions prove the old Chrysler Corporation's engineering superiority that incorporated the principle of applying the simplest, most durable and cost-effective solution to resolve a problem (in this case, manual shifting). In an era when people were tired of standard shifts, they flocked to GM's hydramatic cars, only to find that they needed complete and very expensive tear-down and rebuilds after as little as 20,000 miles. The Chrysler Fluid Drive/3 speed needed no maintenance over and above that required for a standard car, and the semi-automatic Fluid Drives needed very little maintenance compared to the early hydramatics. Many semi-automatic Chrysler Corp. cars are still on the road today and have never had a transmission rebuild, proving the old Chrysler Corp.'s commitment to engineering and design simplicity.
Text of a 1941 Dodge Fluid-Drive brochure
Fifteen operations are necessary to start a car and get into high gear in the usual way. Compare this exhausting routine to the simple operations with Fluid Drive in the new 1941 Dodge Luxury Liner. With Dodge Fluid Drive, you can start in high, STOP in high and start again in high ... without shifting gears! You can drive for hours at varying speeds from as slowly as a mile an hour to your car's top speedall in high gear! Here's the comparison:
In my opinion, it has been years since the automobile industry has produced an operating improvement as revolutionary as the Fluid Drive, now offered for the first time in the low-priced field on the 1941 Dodge.
My long association with and my keen, natural interest in this field of transportation makes me seek an apt comparison which the average person who is not an engineer will understand.
I believe the majority of car owners are parents. At least, they have reached their majority in years. As parents, they appreciate that children seem to grow in jumps.
Children go along for months without any apparent change, and then-all of a sudden-the older folks realize that Johnny is fast outgrowing his clothes; and that Mary, who only yesterday was screaming in her crib, is still screaming-but this time for an evening dress.
It seems to me that automobiles have "grown" in much the same way-by a succession of giant strides in the form of basic developments, each one of which has added tremendously to the ease, the comfort, the economy, the safety of driving a car.
I am particularly happy to say a word here about Dodge Fluid Drive, because the engineers of Dodge enjoy a reputation as pioneers in a number
of those advancements which have helped make the automobile what it is today.
For example, with the great emphasis that they have always placed on the preciousness of human life, the engineers of Dodge gave the world such fundamental improvements as All Steel Bodies and Hydraulic Brakes-both magnificent contributions to your safety in driving.
Now they bring a great new advancement to the low price field! Only this time, their contribution emphasizes greater ease and pleasure in driving-a "consummation devoutly to be wished."
This brochure brings you news of achievement as significant to me as these others of which I have spoken. For it deals with the NEW and BETTER WAY to run an automobileby Fluid Driving.
From the questions so frequently asked of me, I judge that there is widespread curiosity as to how Dodge Fluid Drive differs from other methods of power transmission. The fundamental change is an elimination of the fixed mechanical connections between the engine and the driveshaft. In place of this, a new and far more flexible medium is used-namely, a BODY OF OIL.
Picture yourself at the wheel of a Dodge equipped with Fluid Drive. You step on the starter and, the minute she "purrs," shift right into high gear. Soon as you're ready to
move, release your clutch and step on the accelerator. Immediately, as if soaring away on an invisible cloud, the car sweeps smoothly forward. Not a jolt or a jar -no "bucking" such as would happen with conventional cars if you attempted to start in high. It's the smoothest, cleanest, most noiseless getaway imaginable!
How about stopping? That's even simpler. You merely apply your brake gently as usual but don't touch your clutch or gear lever. Don't bother to shift at all. Stay right in high gear, even when coming to a complete stop.
With Dodge Fluid Drive, your brake keeps the car from moving, even though it is in gear. And despite this, the engine will not stall.
All this means that you can start in high, stop in high, and start right out again in high-without ever shifting gears unless you want to. It means that you can drive all day under ordinary conditions without touching your gearshift or your clutch pedal. In densest traffic where you may often have to throttle down to a speed of a mile an hour-where you are constantly compelled to pause and shift with a conventional transmission -Dodge Fluid Drive permits you to stop and go at will merely by braking or accelerating as the case may be.
Another tremendous advantage comes when your Dodge runs into soft sand or mud holes or deep snow heaps. No doubt you've had the discouraging experience of seeing your
wheels spin around aimlessly without your car budging an inch. Perhaps you've had to call for a tow car to free you from this awkward situation.
With Dodge Fluid Drive, remember, there's a cushion of oil to absorb the sudden surge of engine power which is the cause of wheelspin without gaining traction. Now, the power is applied so smoothly and evenly that you can creep right out of these "tight" places without difficulty. By the same token, on icy roads or streets Dodge Fluid Drive will save you this same annoyance; and the cushioned power goes far to eliminate the frequent cause of skidding.
And what a pleasure when driving on hills! The car can slow
down to a mile an hour in high gear with no danger of stalling the motor. Think of the feeling of security that gives you! Then, coming down hill Fluid Drive is an automatic speed check with the engine acting as a brake, the same as with other methods of transmission.
Understand-despite these many advantages, there is nothing new to learn about Fluid Driving with Dodge. Simply far less work at the wheel. And far smoother performance. The clutch
pedal is there as always. The gearshift lever, too-right on the steering post. The big difference is that under ordinary driving conditions you don't have to use them unless you want to.
When Dodge Fluid Drive was first demonstrated to me, I was thrilled. But more than this, I was consumed with curiosity. I couldn't rest until I saw what made it work. And I believe many of you will react the same way.
It is really very simple. In fact, that very virtue is its strongest recommendation. For there is practically nothing to get out of order or require adjustment or replacement throughout the life of the car.
Fluid Drive, in a word, takes the place of the conventional flywheel in power transmission. There are but two moving parts and even these two never touch-never are subjected to the wear that cannot be avoided where parts are moving and creating friction.
What Fluid Drive Looks Like and How It Works
These moving parts are merely two bowl-shaped shells of steel almost identical in appearance, into which a series of evenly spaced blades or fins are welded. Imagine an orange cut into halves and you have the picture, except that the "halves" of Dodge Fluid Drive measure about thirteen inches in diameter.
One 'of these halves is mounted at the end of the engine crankshaft, its open end facing toward the rear. This is called the driver or impeller. The second half, or runner, is mounted on the propeller shaft, its open end facing the impeller-almost, but not quite, touching it.
A tightly sealed, close-fitting steel housing surrounds these two Fluid Drive parts. The interior is filled with two gallons of a special grade of oil with very low viscosity, so that the impeller and runner are completely submerged.
I have stated that a small gap exists between these two parts.
Now picture what happens when the engine is running. The impeller naturally turns because it is fixed on the crankshaft. This rotating action throws the oil by centrifugal force against the fins of the runner, causing them to rotate in the same direction. It is exactly like one electric fan forcing a current of air against another idle fan and setting the latter in motion-just as a breeze turns a windmill. Only the medium of motion is oil in this case-NOT AIR.
After the engine has picked up speed, the car moves much as it would if this "fluid coupling" were mechanical. One important and very noticeable difference is that you experience no jarring or jerking. Not only in starting, but in driving and stopping, the motion is emphatically smoother.
Perhaps the most astonishing difference in Fluid Driving with Dodge is the marked increase in flexibility and control. This is due to the fact that impeller and runner may now travel
at different speeds. This Dodge with Fluid Drive may be started, driven for hours, stopped repeatedly in traffic, and started over and over again always remaining in high gear. It is like having a car of literally limitless speeds in this one gear.
The experience of thousands of motorists, once they try Dodge Fluid Driving, is that ninety per cent of the work is eliminated. The whole operation becomes simpler, safer, more pleasurable and relaxing in the 1941 Dodge with Fluid Drive than was ever before possible in a low-priced car.
Before you buy your new car, let me urge you to go for a ride with Dodge Fluid Drive. I promise you it will be an altogether thrilling experience.
Here's what Dodge had to say about their "all fluid drive" in a different brochure:
S. Berliner III wrote:
S. Berliner III noted that Fluid Drive was trade-named Gyról Fluid Drive, a meaningless Frenchified word.
Fluid drives on trucks
Paul Sahler wrote: "I believe it was offered as an option in 1948-52 1/2 ton pickups I have seen and driven both the 3 speed on the column and a 4 speed on the floor. They used standard truck transmissions with longer input shafts and the bell housing is a longer cast piece.
"You can push start a Fluid Drive vehicle using 2nd gear in the three and four speeds and 2nd gear low range in the wait and clunk, starting with the clutch depressed at about 15 mph ease the clutch out. If you start with the clutch out you need to reach 20-25 mph before the oil in the fluid drive has enough oomph to spin the engine.
"As far as pulling power in the pickups, not a problem, we regularly pulled 4-41/2 tons of hay with a four speed 1/2 ton. Dad and I also used to put a yard of gravel on this same truck. I have wondered how a fluid drive would do in a military style Power Wagon. The action of the Fluid Drive seems like it would work real well in low speed rock and hill applications. The other nice thing is I don't ever remember replacing a clutch in any of our Fluid Drive Mopars."
Paul Sahler added:
People need to remember that before the mid-1950s Fluid Drives were not transmissions, they were couplings between the engine and clutch, the shared oil ones were an attempt to build torque by using pressurized oil. The only basic difference in the pre-1950s transmissions, between the fluid drives and non fluid drives, is the length of the input shaft, fluid drives shafts are longer to reach the pilot shaft bushing. The bell housing is also longer to accept the thicker fluid drive unit.
I remember getting four shifts in a 1948 New Yorker straight 8, however Dad had mentioned something about it not being quite right, to correct the problem he wired some switches and the car could be driven both ways. By using the correct switch and revving the motor at the same time, you could downshift to low range and use engine-braking to help you to stop. Helpful in a 2 ton car.
I do agree that the shared-oil fluid drives were in more than the Plymouths. When Dad would come across those years cars, that was one of the things he would look for. He did not want a car that the oil is shared, to easy for things to go wrong in his opinion.
What makes them different to most people is the ability to be in gear with your foot on the brake not the clutch. Although difficult you could stall the motor by dumping the clutch and if you tried real hard you could spin the tires. And if you want to really have fun with someone who has never seen one, with the motor running, making sure they notice, put the car in gear, with your foot on the brake, ease the clutch out, then ask them what's wrong. One person was so convinced the clutch was slipping he walked home just so he would make it.
Dave Stragand of forwardlook.net supplied the following notes from current owners:
from Terry and Andree Hoeman: The original intention was to only put it into high range and use the two speed feature in it. Low range was only for high load usage and towing type stuff. We are used to quick acceleration now and feel we must use the low range first. I bet it doesn't add much to speed up the start up when you throw in the slow shift time from low to high range.
from Tom Stroup: We have a 1948 DeSoto and you have described (shifting) it perfectly. Put stick in second gear position, start out, lift foot on accelerator, hear the clunk, go some more, shift into third gear position.
from Semodave: Technique to get all 4 speeds was start in 1st, rev to 25mph; clutch and quickly jerk shifter to just touch "high" then back to 2nd--no clunk here. As more speed was gained, clutch quickly to "high" kicking down in the process, then 4th would come in when you let up on gas--usually around 70! Always used 4 speeds in all races I was in; and usually
won--that 120 mph speedo wasn't just for show.
from S. Keller: I had/drove many Fluid Drives, like this: push in clutch, put in Hi, let out clutch and drive all day. Never used Lo except to squeal the tires to show off in my 1953 Dodge 6 cylinder. Even back then in 1966 my friends couldn't get it, so they had to drive Fords and Chevys.
Stories
George Shahovskoy wrote:
Home •
Engines •
Reviews •
Chrysler 1904-2018 •
Upcoming •
Trucks •
Cars
Spread the word via <!--Tweet or--> Facebook!
We make no guarantees regarding validity or accuracy of information, predictions, or advice - .
Copyright © VerticalScope Inc. All rights reserved. Dodge, Jeep, Chrysler, Ram, and Mopar are trademarks of Fiat Chrysler Automobiles.
by Sam Chase
These cars do not change gears "automatically," but can be held stationary in any gear without disengaging the clutch. They can also be started in any gear without slipping the clutch, although 3rd gear starts are painfully slow. Fluid drive advantages are:
- The car can be driven by declutching and shifting in the normal fashion, starting in 1st, shifting to 2nd, and then to 3rd.
- Downshifts from 3rd to 2nd are greatly reduced.
- In stop-and-go traffic, the car may be left in 2nd gear with the driver starting and stopping merely by applying the foot brake and accelerator pedals, as is done in a car equipped with a modern automatic transmission.
- Acceleration from 5 MPH up in 3rd gear is entirely acceptable under most level-road conditions.
- Ascending moderately steep hills does not require downshifting.
-
- Starting on hills is greatly facilitated. The car may be placed in 1st gear, the clutch engaged, and the car held motionless by application of the foot brake only. When it is time to start, the driver merely steps on the accelerator. There is no need to coordinate the clutch/brake/accelerator with the inevitable engine over-revving and clutch slipping that are the hallmark of manual-shift car hill starts.
- Wear on clutch parts is greatly reduced because there is no need to "slip" the clutch for smooth starts from rest.
- Fluid drive cars have a lower numerical rear axle ratio, thereby reducing constant speed engine RPMs.
There are also disadvantages:
- When starting from rest in 1st gear, "off the line" acceleration suffers because of the "slipping" action of the fluid coupling. This is largely overcome at the point where the car attains a speed of 10-15 MPH, however.
- Leaving the transmission in gear with the engine off does not lock the rear wheels. A fluid coupling car left in gear with the engine off will roll just as if it were left in neutral. Therefore, maintaining the emergency/parking brake is paramount, and care should be taken when parking the car when anything but absolutely level road conditions are encountered.
In 1941, Chrysler offered its "semi-automatic" transmission in combination with the fluid coupling, at considerable (for the time, anyway) extra cost, usually between $100-140 depending on the model on which it was installed. This semi-automatic transmission consists of the fluid coupling, a two-speed manual transmission with integral underdrive, and conventional clutch. The early models (M-4) operate on engine vacuum ("vacamatic"), while the later models (M-5 and M-6) operate on a combination of electric circuitry and hydraulics.
There are four forward gear ratios:
- Underdrive Low: 3.57 to 1.00
- Low: 2.14 to 1.00
- Underdrive High: 1.75 to 1.00
- High (Direct Drive) 1.00 to 1.00
To start the car under normal conditions (relatively flat road, light load), the driver depresses the clutch pedal and shifts into High range. At this point, the transmission is in "Underdrive High" which means that the transmission is in Direct Drive with the underdrive gearing engaged. When a speed of approximately 14 MPH is attained, the driver lifts his foot completely off the accelerator pedal, the underdrive gearing disengages, and the car is now in Direct Drive. If extra pulling power or acceleration is desired from a dead stop or the car is starting from rest on a steep hill, the driver shifts into Low range where the transmission is in Underdrive Low with the underdrive gearing engaged. When the car reaches approximately 6 MPH, the driver lifts his foot off the accelerator, the underdrive disengages, and the car is in Low. At this point a manual shift from Low range to High range (driver steps on clutch pedal and moves shift lever from the "low" to "high" position) brings the car into Direct Drive.
The advantages of this transmission vs. a conventional manual or fully automatic "clutchless" transmission are:
- There is a clutch pedal, affording a driver greater control over the power flow from the engine to the drive wheels.
- The car is normally started in Underdrive High, an advantage in reduced traction situations.
- Manipulation of the clutch pedal and gearshift lever is completely eliminated in normal forward driving once the car has been started from an "engine off" state. Acceleration from rest in Underdrive High is entirely satisfactory under most light-load, level road conditions.
- The driver can directly control the timing of automatic upshifts by use of the accelerator pedal.
- Greatly simplified, rugged construction requiring very little maintenance vs. a 1950Õs fully automatic transmission.
Disadvantages:
- Driver must depress clutch pedal every time the shift lever is moved.
- Changes between "low" and "high" range are completely manual requiring manipulation of the shift lever and clutch pedal.
- Acceleration from Underdrive High and automatic shift into Direct Drive is slower than with a fully automatic transmission.
- As one 1950s car reviewer said, "It has all the disadvantages of a manual shift and automatic car combined."
Chrysler indiscriminately referred to both the standard and semi-automatic fluid-coupling transmissions as "Fluid Drive" in its promotional and technical literature. This contributed greatly to the confusion between the two types, and many Chrysler Corp. car owners of that time did not understand the difference. Many who had the fluid drive/3-speed manual configuration were not aware of any difference between that and the conventional flywheel set-up.
The fluid drive and semi-automatic transmissions prove the old Chrysler Corporation's engineering superiority that incorporated the principle of applying the simplest, most durable and cost-effective solution to resolve a problem (in this case, manual shifting). In an era when people were tired of standard shifts, they flocked to GM's hydramatic cars, only to find that they needed complete and very expensive tear-down and rebuilds after as little as 20,000 miles. The Chrysler Fluid Drive/3 speed needed no maintenance over and above that required for a standard car, and the semi-automatic Fluid Drives needed very little maintenance compared to the early hydramatics. Many semi-automatic Chrysler Corp. cars are still on the road today and have never had a transmission rebuild, proving the old Chrysler Corp.'s commitment to engineering and design simplicity.
Text of a 1941 Dodge Fluid-Drive brochure
Fifteen operations are necessary to start a car and get into high gear in the usual way. Compare this exhausting routine to the simple operations with Fluid Drive in the new 1941 Dodge Luxury Liner. With Dodge Fluid Drive, you can start in high, STOP in high and start again in high ... without shifting gears! You can drive for hours at varying speeds from as slowly as a mile an hour to your car's top speedall in high gear! Here's the comparison:
THE MAGIC OF FLUID-DRIVE (BY MAJOR EDWARD BOWES)
My long association with and my keen, natural interest in this field of transportation makes me seek an apt comparison which the average person who is not an engineer will understand.
I believe the majority of car owners are parents. At least, they have reached their majority in years. As parents, they appreciate that children seem to grow in jumps.
Children go along for months without any apparent change, and then-all of a sudden-the older folks realize that Johnny is fast outgrowing his clothes; and that Mary, who only yesterday was screaming in her crib, is still screaming-but this time for an evening dress.
It seems to me that automobiles have "grown" in much the same way-by a succession of giant strides in the form of basic developments, each one of which has added tremendously to the ease, the comfort, the economy, the safety of driving a car.
I am particularly happy to say a word here about Dodge Fluid Drive, because the engineers of Dodge enjoy a reputation as pioneers in a number
of those advancements which have helped make the automobile what it is today.
For example, with the great emphasis that they have always placed on the preciousness of human life, the engineers of Dodge gave the world such fundamental improvements as All Steel Bodies and Hydraulic Brakes-both magnificent contributions to your safety in driving.
Now they bring a great new advancement to the low price field! Only this time, their contribution emphasizes greater ease and pleasure in driving-a "consummation devoutly to be wished."
This brochure brings you news of achievement as significant to me as these others of which I have spoken. For it deals with the NEW and BETTER WAY to run an automobileby Fluid Driving.
From the questions so frequently asked of me, I judge that there is widespread curiosity as to how Dodge Fluid Drive differs from other methods of power transmission. The fundamental change is an elimination of the fixed mechanical connections between the engine and the driveshaft. In place of this, a new and far more flexible medium is used-namely, a BODY OF OIL.
Picture yourself at the wheel of a Dodge equipped with Fluid Drive. You step on the starter and, the minute she "purrs," shift right into high gear. Soon as you're ready to
move, release your clutch and step on the accelerator. Immediately, as if soaring away on an invisible cloud, the car sweeps smoothly forward. Not a jolt or a jar -no "bucking" such as would happen with conventional cars if you attempted to start in high. It's the smoothest, cleanest, most noiseless getaway imaginable!
How about stopping? That's even simpler. You merely apply your brake gently as usual but don't touch your clutch or gear lever. Don't bother to shift at all. Stay right in high gear, even when coming to a complete stop.
With Dodge Fluid Drive, your brake keeps the car from moving, even though it is in gear. And despite this, the engine will not stall.
All this means that you can start in high, stop in high, and start right out again in high-without ever shifting gears unless you want to. It means that you can drive all day under ordinary conditions without touching your gearshift or your clutch pedal. In densest traffic where you may often have to throttle down to a speed of a mile an hour-where you are constantly compelled to pause and shift with a conventional transmission -Dodge Fluid Drive permits you to stop and go at will merely by braking or accelerating as the case may be.
Another tremendous advantage comes when your Dodge runs into soft sand or mud holes or deep snow heaps. No doubt you've had the discouraging experience of seeing your
wheels spin around aimlessly without your car budging an inch. Perhaps you've had to call for a tow car to free you from this awkward situation.
With Dodge Fluid Drive, remember, there's a cushion of oil to absorb the sudden surge of engine power which is the cause of wheelspin without gaining traction. Now, the power is applied so smoothly and evenly that you can creep right out of these "tight" places without difficulty. By the same token, on icy roads or streets Dodge Fluid Drive will save you this same annoyance; and the cushioned power goes far to eliminate the frequent cause of skidding.
And what a pleasure when driving on hills! The car can slow
down to a mile an hour in high gear with no danger of stalling the motor. Think of the feeling of security that gives you! Then, coming down hill Fluid Drive is an automatic speed check with the engine acting as a brake, the same as with other methods of transmission.
Understand-despite these many advantages, there is nothing new to learn about Fluid Driving with Dodge. Simply far less work at the wheel. And far smoother performance. The clutch
pedal is there as always. The gearshift lever, too-right on the steering post. The big difference is that under ordinary driving conditions you don't have to use them unless you want to.
When Dodge Fluid Drive was first demonstrated to me, I was thrilled. But more than this, I was consumed with curiosity. I couldn't rest until I saw what made it work. And I believe many of you will react the same way.
It is really very simple. In fact, that very virtue is its strongest recommendation. For there is practically nothing to get out of order or require adjustment or replacement throughout the life of the car.
Fluid Drive, in a word, takes the place of the conventional flywheel in power transmission. There are but two moving parts and even these two never touch-never are subjected to the wear that cannot be avoided where parts are moving and creating friction.
What Fluid Drive Looks Like and How It Works
These moving parts are merely two bowl-shaped shells of steel almost identical in appearance, into which a series of evenly spaced blades or fins are welded. Imagine an orange cut into halves and you have the picture, except that the "halves" of Dodge Fluid Drive measure about thirteen inches in diameter.
One 'of these halves is mounted at the end of the engine crankshaft, its open end facing toward the rear. This is called the driver or impeller. The second half, or runner, is mounted on the propeller shaft, its open end facing the impeller-almost, but not quite, touching it.
A tightly sealed, close-fitting steel housing surrounds these two Fluid Drive parts. The interior is filled with two gallons of a special grade of oil with very low viscosity, so that the impeller and runner are completely submerged.
I have stated that a small gap exists between these two parts.
Now picture what happens when the engine is running. The impeller naturally turns because it is fixed on the crankshaft. This rotating action throws the oil by centrifugal force against the fins of the runner, causing them to rotate in the same direction. It is exactly like one electric fan forcing a current of air against another idle fan and setting the latter in motion-just as a breeze turns a windmill. Only the medium of motion is oil in this case-NOT AIR.
After the engine has picked up speed, the car moves much as it would if this "fluid coupling" were mechanical. One important and very noticeable difference is that you experience no jarring or jerking. Not only in starting, but in driving and stopping, the motion is emphatically smoother.
Perhaps the most astonishing difference in Fluid Driving with Dodge is the marked increase in flexibility and control. This is due to the fact that impeller and runner may now travel
at different speeds. This Dodge with Fluid Drive may be started, driven for hours, stopped repeatedly in traffic, and started over and over again always remaining in high gear. It is like having a car of literally limitless speeds in this one gear.
The experience of thousands of motorists, once they try Dodge Fluid Driving, is that ninety per cent of the work is eliminated. The whole operation becomes simpler, safer, more pleasurable and relaxing in the 1941 Dodge with Fluid Drive than was ever before possible in a low-priced car.
Before you buy your new car, let me urge you to go for a ride with Dodge Fluid Drive. I promise you it will be an altogether thrilling experience.
Here's what Dodge had to say about their "all fluid drive" in a different brochure:
More details
S. Berliner III wrote:
Bill Watson wrote:
"68RT" write:
Mike Sealey clarified:
Bill Watson wrote:
Ron Riopelle:
Charlie Pfefferkorn: "In the early 1960s, my 1953 Firedome needed a little extra help. By placing a switch in line with the kick down circuit, I was able to use all four speeds. After the pause shift from low-low to low-high, I would then throw the switch as the shift lever passed neutral. The Desoto was then in hi-low with the next shift the normal pause shift into hi-hi. The switch had to be turned off any time before the last shift or it would just free wheel after letting off the gas peddle. The best acceleration was achieved by short shifting lo-lo to lo-hi. The split shift was the quickest. Then wait forever for hi-hi. I drove it like that for a long time with no trans trouble."
S. Berliner III noted that Fluid Drive was trade-named Gyról Fluid Drive, a meaningless Frenchified word.
Fluid drives on trucks
Paul Sahler wrote: "I believe it was offered as an option in 1948-52 1/2 ton pickups I have seen and driven both the 3 speed on the column and a 4 speed on the floor. They used standard truck transmissions with longer input shafts and the bell housing is a longer cast piece.
"You can push start a Fluid Drive vehicle using 2nd gear in the three and four speeds and 2nd gear low range in the wait and clunk, starting with the clutch depressed at about 15 mph ease the clutch out. If you start with the clutch out you need to reach 20-25 mph before the oil in the fluid drive has enough oomph to spin the engine.
"As far as pulling power in the pickups, not a problem, we regularly pulled 4-41/2 tons of hay with a four speed 1/2 ton. Dad and I also used to put a yard of gravel on this same truck. I have wondered how a fluid drive would do in a military style Power Wagon. The action of the Fluid Drive seems like it would work real well in low speed rock and hill applications. The other nice thing is I don't ever remember replacing a clutch in any of our Fluid Drive Mopars."
Paul Sahler added:
People need to remember that before the mid-1950s Fluid Drives were not transmissions, they were couplings between the engine and clutch, the shared oil ones were an attempt to build torque by using pressurized oil. The only basic difference in the pre-1950s transmissions, between the fluid drives and non fluid drives, is the length of the input shaft, fluid drives shafts are longer to reach the pilot shaft bushing. The bell housing is also longer to accept the thicker fluid drive unit.
I remember getting four shifts in a 1948 New Yorker straight 8, however Dad had mentioned something about it not being quite right, to correct the problem he wired some switches and the car could be driven both ways. By using the correct switch and revving the motor at the same time, you could downshift to low range and use engine-braking to help you to stop. Helpful in a 2 ton car.
I do agree that the shared-oil fluid drives were in more than the Plymouths. When Dad would come across those years cars, that was one of the things he would look for. He did not want a car that the oil is shared, to easy for things to go wrong in his opinion.
What makes them different to most people is the ability to be in gear with your foot on the brake not the clutch. Although difficult you could stall the motor by dumping the clutch and if you tried real hard you could spin the tires. And if you want to really have fun with someone who has never seen one, with the motor running, making sure they notice, put the car in gear, with your foot on the brake, ease the clutch out, then ask them what's wrong. One person was so convinced the clutch was slipping he walked home just so he would make it.
Dave Stragand of forwardlook.net supplied the following notes from current owners:
from Terry and Andree Hoeman: The original intention was to only put it into high range and use the two speed feature in it. Low range was only for high load usage and towing type stuff. We are used to quick acceleration now and feel we must use the low range first. I bet it doesn't add much to speed up the start up when you throw in the slow shift time from low to high range.
from Tom Stroup: We have a 1948 DeSoto and you have described (shifting) it perfectly. Put stick in second gear position, start out, lift foot on accelerator, hear the clunk, go some more, shift into third gear position.
from Semodave: Technique to get all 4 speeds was start in 1st, rev to 25mph; clutch and quickly jerk shifter to just touch "high" then back to 2nd--no clunk here. As more speed was gained, clutch quickly to "high" kicking down in the process, then 4th would come in when you let up on gas--usually around 70! Always used 4 speeds in all races I was in; and usually
won--that 120 mph speedo wasn't just for show.
from S. Keller: I had/drove many Fluid Drives, like this: push in clutch, put in Hi, let out clutch and drive all day. Never used Lo except to squeal the tires to show off in my 1953 Dodge 6 cylinder. Even back then in 1966 my friends couldn't get it, so they had to drive Fords and Chevys.
Stories
George Shahovskoy wrote:
- Hy-Drive transmission
- Powerflite transmission
- Engines and transmissions page
- Still want more on the Fluid Drive? See this 1948 brochure posted at the Imperial Club site!
Home •
Engines •
Reviews •
Chrysler 1904-2018 •
Upcoming •
Trucks •
Cars
Spread the word via <!--Tweet or--> Facebook!
We make no guarantees regarding validity or accuracy of information, predictions, or advice - .
Copyright © VerticalScope Inc. All rights reserved. Dodge, Jeep, Chrysler, Ram, and Mopar are trademarks of Fiat Chrysler Automobiles.