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41 Chrylser Blues.........


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For the past two years I have been experiencing problems with the fluid-drive gearbox in my 41 Chrysler Royal.


Now I don't profess for one minute to understand all that much about vehicle mechanics (even less about how such an unusal gearbox actually works) despite Ed Abbott's best efforts and fag-packet diagrams to try and explain.


The problem.


When the car is cold, its all fine. I can do maybe 15 miles before things start to happen - which is why the problem doesn't actually stop me from using the car and why when we got married last year, we chose a wedding venue only 1/2 a mile from our house, so we could use the Chrysler on our Wedding Day.....!!


But I digress. After around 15 miles (less on a hot day) the car all of a sudden changes down to second and will not go into top. The car only has three forward gears and the fluid drive enables you to drive away in first, dip the clutch and drop it into second, accelerate in second and when you let your foot off the throttle, the car automatically drops into top without any clutch or gearshifting. Similarly, when you stop at a set of traffic lights and you are in second gear, you do not need to depress the clutch, just the brake. The car sits at the lights in gear, and when you pull away you just release the brake and hit the gas.


But, the problem is not getting any better, in fact quite the opposite and I am now feeling that I must try and get the problem sorted, rather than plan my weekends around the vehicles limitations! Once it has (theoretically) lost top gear I can still do about 45, but the car is revving too high in second. The alternative I then have is to pull a manual cable knob on the dash (which says it is only to be engaged when the vehicle is being towed) and this pulls a metal cable which is linked to a mechanism which sits on the side of the gearbox. Pulling this disengages this mechanism, which then allows the car to jump into top and then we can fly along. The down side is that having done this, the car then looses first gear and you can only use second and third, which by and large is ok, but when I pulled the caravan up to to North Norfolk 40's weekend in September and when we hit a particularly steep hill on the back road to Holt in the dark, I didn't think the old girl was going to crest the hill in second, and I had no more gears left! In the dark, with the children aboard and on a dangerous stretch of minor road with poor lights, my heart was a thumping and I vowed that if we made the hill, I wouldn't put my family in that tight spot again.........So I need to get it sorted.


As I say, I haven't got the know-how myself, so I know I will need to engage a specialist company, but it would help if I could give them an idea of where the problem may lie - It may also help my cheque-book!


Does anyone have any knowledge of this kind of transmission system or can recommend any specialist who may be able to get to the bottom of the problem. Alternatively, the car was manufactured in 41 and the fluid-drive was an option. Could I source a standard gearbox and replace it with that, if this is going to work out more reliable and a more cost effective option.


I have no intention of selling the car as we all love using it and it is so comfortable to attend shows and rallies with the whole family, so have no concern in telling the MV world about my vehicle woes!


Any advice would be much appreciated.


A couple of pictures to show you why we love the old girl so much!



Ed Abbott's Wedding.



Shame about that aircraft spoiling a nice shot of the car!



New paintwork (Summer 2010)

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Well -


If I hadn't lent my 1953 copy of 'Motor's Auto Repair Manual' to a certain person - who then gave it to someone else to decypher - (and where is it now I might ask?), I just might have been able to help you.....




Can I suggest you get the manual back first :-D

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You'll be delighted to know Tony that the very manual in question was returned to me all safe and well last Friday by a certain member of the Norfolk Constabulary, on duty, in uniform and in his official mode of transport!


The curtains were twitching next door and he only came around to drop the book off and drink tea..........at the tax payers expense I might add!


No wonder the country is going to the dogs.......

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You say it is alright until you have done about 15 miles........this makes me wonder if it is the wrong grade / type of oil and once it gets hot, the problems start. It is doubtfull that the original specification was for an auto transmission fluid, probably used a straight grade engine oil. So do you know what it is filled with? If not, then suggest you renew the oil first, according to the vehicle's manual.


regards, Richard

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You say it is alright until you have done about 15 miles........this makes me wonder if it is the wrong grade / type of oil and once it gets hot, the problems start. It is doubtfull that the original specification was for an auto transmission fluid, probably used a straight grade engine oil. So do you know what it is filled with? If not, then suggest you renew the oil first, according to the vehicle's manual.


regards, Richard


Hey Clive


Isn't that exactly what Steve, Kevin and myself suggestted two years ago!!!!

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Hey Clive


Isn't that exactly what Steve, Kevin and myself suggestted two years ago!!!!


No. Two years ago you suggested changing the oil (which I believe Ed Abbott had done when he serviced it before his wedding) not changing the grade/type of oil as Richard has suggested here.


Don't forget your talking to someone with limited knowledge and who is guided by those with greater know-how. If an experienced life-long Engineer like Ed say's to me "I've changed the oil,' who am I to argue with that?


Thanks for the input thus far guys (and for NOS telephone diagnostic's tonight!)

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Just look at how complex that flow chart is :shocked: But they do say all you need for diagnostics is a test lamp and a pressure gauge :D


Could be changing gear through either oil pressure (should be 40psi at 15mph - pump driven off gearbox mainshaft so no vehicle movement = no oil flow) or faulty electrics(solenoid breaking down etc).


Can't advise more without the manual. Let's hope Richard is on the money!





Fluid-Drive Flow Chart.JPG

Fluid-Drive Diagnostics.JPG

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OMG there's even a support group out there!!!






and here is some info on the transmission, check out the bottom of page, oil grades for the different types of transmissions..........



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That link Richard is a page taken from the either the 'Motor's Auto Repair Manual' I mentioned above (which has apparently just been returned to its foster dad by a policeman? - what is going on - does it now have an ASBO stamp on the flyleaf?), or more likely the New Thompson Repair and Tune-Up Manual (see below) - as page layout style is same as the truck vol.2.


I've had a 1957 copy of Motor's for a long time - but it only covers 1949 through 1957, so I managed to pick up an earlier edition which covers all ww2 era vehicle mechanics.


It really is a great 'bible' for U.S. vehicles, a sort of condensed repair manual which gives the essential bits of info. Useful snippets of info like - from the 1957 description of the Fluid Drive trans (a later 4 speed version? - or should you have another gear Clive? We need to look at those manuals I think!) -


" The main thing to remember is that the transmission electrical system is used to keep the trans. in third or first speed gear depending on gear shift lever pos., and that the hydraulic control system is used to keep the trans. in second or fourth speed gear, depending on position of gear shift lever"

I also have one for trucks 1940 through 1949 called The New Thompson Repair and Tune-Up Manual' Vol 2 (Vol 1 was passenger cars) - this covers engines, transmission, axles, steering gear.


I can highly recommend these, not just for a specific vehicle, but as a good read - a fascinating insight into automotive engineering practises of the era (when most of the main truck manufacturers were building their own engines). Seems they were printed every year and covered a 10 year span of vehicle models.

Edited by N.O.S.
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There is some good info on Wikipedia, and I've lifted some out here. Note the bit in red, which caught my eye and may give a clue as to the source of your problem Clive?


Fluid Drive
is the
name that
Chrysler Corporation
assigned to a transmission driveline combination offered from 1939 through 1953 in Chryslers, 1940 through 1953 in
, and from 1941 through 1954 in
models. The fluid drive element was a
hydraulic coupling
inserted in place of the
, and performed the same function as a modern
torque converter
, only without torque multiplication. A conventional
and three-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 1900’s. 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
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
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 third gear without using the clutch and proceed without downshifting. 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
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 cheaper than a
, 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


Main articles:
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 speeds in 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
fully automatic, clutchless
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.


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