1947 Dodge fluid drive

[Johnboy]

Hi my friend has a 1947 Dodge 4 door fluid drive. What type of fluid goes in the transmission. Where do I check it. He has no power going up hills he thinks he is low on transmission fluid. Thanks

[wagoneer]

Mobil one DTE light recirculating fluid

 

From @MarcDeSoto

 

I'm one of the guys who had a big thread on this subject.   You're right, you can't look up past threads very well here.   James did a long study and research on this question and came up with this product.  Mobil Light Circulating Oil ISO 32.  This product is difficult to look up.  I tried searching for it on Amazon and it gave many look alike Mobil oils, but NOT the right one.  I had to look up my order from Grainger's and use the product number to look it up on Amazon.  I saved a few bucks by driving 30 miles to the my local Grainger's, but even they had to order it.  You might well say that this is just 10W oil so why not put 10W motor oil in the fluid drive like you do in the semi auto transmission.  Well, because it won't work well.  This oil has anti-foaming agents to prevent  cativation in the fluid drive, which will cause the car to have poor acceleration and slipping.  It's because this oil is made for turbines that it works well in the fluid drive coupling.  It does not come in one gallon sizes, so you have to buy more than you  really need, which is just under two gallons.  

 

https://www.amazon.com/Mobil-DTE-Light-ISO-gal/dp/B07CSLKT1J/ref=pd_rhf_se_p_img_2?_encoding=UTF8&psc=1&refRID=HMVQFANK8D7F8CYKVMYX#descriptionAndDetails

[busycoupe]

There  is an inspection cover under the front mat/carpeton the top right sideof the transmision hump. When you remove the cover you can see the fluid drive unit.  The unit has two fill/drain ports on opposite sides of the unit.  You need to turn motor either by bumping the starter or by turning the fan until one of the fill ports lines up with the inspection opening.   Then you can use a socket wrench to open the fill port.  Stuff a rag around the opening so that if you drop the plug it won't fall down in the bell housing out of reach.  The fluid should be filled to the edge of the fill port.  As Wagoneer says above, you should use Mobil 1 light recirculating fluid. However, I and many others have also used universal tractor fluid # 134.  This is an iso 32 wt. hydraulic fluid and works in the fluid drive unit just fine.  You can get it at Tractor Supply and many auto parts stores. 

Several years ago my 48 Dodge was slipping going up hill and I found I had to add 2 qts of fluid.  It has been fine since.

Edited August 14, 2021 by busycoupe

[Johnboy]

Thanks guys for the info. Another question If I fill the fluid drive is that separate than the transmission or all one unit.

[busycoupe]

On the 47 Dodge the fluid drive is entirely separate from the transmission.  Some Mopars from the early 50's had a transmision and coupling that shared oil.

[Johnboy]

Thanks Busycoupe if I want to drain fluid drive is it done under car, and does it hold 2 gallons. 1 gallon on each side.

[busycoupe]

Yes, you do drain it from under the car. When I said that there are two fill ports I meant that they are 180 degrees apart. on opposite sides of the unit.  The unit is all one piece, all fluid together.     It is generally not necessary or adviseable to drain the fluid drive unit.  Topping off is all that is usually needed.  

[greg g]

Stop!  The fluid drive unit and transmission are two distinct assemblies with two separate fluid needs.  Actually three depending if the car is equiped with the gyro matic semi auto transmission  or the three speed manual.  None of them have any thing to do with hillclimbing power.  The fluid drive fluid was a proprietary fluid and isn't available any more.  It was a life time fill and no service was required unless there was a leak. There is an acces panel in the floor up by the fire wall where fluid level can be checked.  Today the closest substitute is universal tractor hydraulic fluid.  However conventional wisdom is to add if needed to bring it to operating level, rather than draining the original fluid.

 

 Note operating level is not briming full.  Some space is required for expansion of fluid from heat. An over filled unit will lead to failed seals due to excess pressure from expansion.

 The seals are serviceable but you don't want to go there unless absolutely necessary. 

 

The semi auto trans called for SAE 10 non detergent motor oil.

 

The manual three speed calls for SAE 90 GL1 rated gear oil, or some have found good service from SAE 10 motor oil.  There are compounds in modern gear lube that aren't friendly with brass, bronze synchro parts so newer than gl 1 isn't recommended.

 

Further identification of which units you are dealing with before picking up tools and adding the wrong stuff in the wrong place.  If you decide to open the fluid drive unit DO NOT DROP THE PLUG into the housing.

Edited August 14, 2021 by greg g

[busycoupe]

Johnboy said that  he was dealing with a 47 Dodge.  The 46-48 Dodges only came with a  3 speed manual, or a 3 speed manual with a  fluid drive coupling.  A car with a fluid drive coupling that is low on fluid will feel like a car with a slipping clutch. It is impossible to overfill the fluid coupling.  The position of the access cover in the passenger floor is such that the fill port on the coupling is at the correct angle to leave air space at the top of the coupling when ig is filled.

[knuckleharley]

18 minutes ago, busycoupe said:

Johnboy said that  he was dealing with a 47 Dodge.  The 46-48 Dodges only came with a  3 speed manual, or a 3 speed manual with a  fluid drive coupling.  A car with a fluid drive coupling that is low on fluid will feel like a car with a slipping clutch. It is impossible to overfill the fluid coupling.  The position of the access cover in the passenger floor is such that the fill port on the coupling is at the correct angle to leave air space at the top of the coupling when ig is filled.

What about the 1942 Dodges?

[Dodgeb4ya]

2 hours ago, knuckleharley said:

What about the 1942 Dodges?

 

Same service procedures as thenD24 Dodge cars 

[knuckleharley]

52 minutes ago, Dodgeb4ya said:

 

Same service procedures as thenD24 Dodge cars 

Thanks!

[greg g]

I have heard of people jury rigging tubes, drilling auxiliary holes, etc to try to get the fluid level as high as they can. Thinking the more the merrier when it comes to how much to put in.  Not sure the capacity of the threespeed manual but it's way less than 2 gallons.

[Johnboy]

Hi thanks everyone for your help. I have one more question. Does the 47 Dodge fluid drive have any adjustments.

[busycoupe]

The fluid drive unit has no adjustments. There are however, adjustments on the shift linkage going to the transmission and on the clutch linkage. 

[Johnboy]

Busycoupe and others thanks for all your help. 

[greg g]

What area of NY are you from?

[Doug&Deb]

Do you have a service manual? Any clutch and shift linkage adjustment is covered. Reprinted manuals are inexpensive and highly recommended. Meanwhile keep asking questions. These guys know there stuff.

[Johnboy]

Greg g I’m in Lexington NY. Doug & Deb the 47 is a friends car I will tell him to look for a manual. This club is great. It is full of smart and knowledgeable members. Thanks

[MarcDeSoto]

Don't forget to check out the excellent resources at MyMopar where they have the original Master Tech videos going back to 1947 that Chrysler mechanics watched.  This filmstrip is about the Chrysler DeSoto semi-auto transmission, but you can go back to select other filmstrips.  https://mymopar.com/mtsc-1948-volume-a-the-hydraulically-operated-transmission/

[James_Douglas]

I do love it when people say to never drain the fluid coupling and refill it and that it is a sealed for life unit. The conversation I had 10 years ago with the technical head of Gyrol is in direct conflict with that advice.

 

If folks are going to give such advise, then please provide the reasoning behind it. Since the unit efficiency depends entirely on the fluid velocity...anything that slows that velocity robs power. A fluid without the proper amount of anti-foaming agent will rob power. The anti-foaming agents have a life span of 7 years at most according to Gyrol. Even in the can. There are also additives to raise the VI and those two break down over time as well. So do the anti-corrosion additives that protect that bearing that cannot be changed for less that a couple of grand.

 

In addition to all of that the engineer made it clear that the steel is not 100% vapor tight. It does at the molecular level allow for minute amounts of water vapor to move in and out of the steel. Now this is VERY small amounts but over decades he has seen enough to affect the bearing. Another reason to change the fluid every seven or so years.

 

Since Gyrol was the folks who licensed the technology to Chrysler in the first place and they still make industrial fluid couplings, I would listen to such advice. That is why I went to the trouble to do the write up on the fluid.

 

Telling people not to change it is bad advise as far as I can find based on the science of how they work and the practical experience of the people who still make them. If one really thinks it is is bad advise to change the fluid then by all means please marshal some evidence to support that potion based on the science of how the coupling works and the like. I would like to read the reasoning.

 

James

 

 

 

 

 

[Dodgeb4ya]

I have never changed the fluid in any of my Chrysler 8 cylinder FD cars.

I've also never ever had a failure in any of said couplings.

I've owned these cars over 40 years. 

Now... I do service engine oil, auto trans, brake and coolant fluids more often than most people.

 

 

[wagoneer]

In principle, the fluid coupling fluid should be changed at some service point, as every part of every machine needs service or wholesale replacement at some point.

 

I think the barrier at this moment is not the changing but the cost to change due to the current recommended fluid coming in 5 gallon quantities and $160.

 

torque converter and trans fluid is replaced periodically , why not this other fluid coupling. 
 

maybe if the fluid didn’t move or potentially degrade it really could be lifetime, but the life of a vehicle was on the order of 10 years then, not 75.

[Johnboy]

Wagoneer I’m going to look at the oil in granger, I tried tractor supply with # from Busycoupe couldn’t find it. This is my friends car talked to him today bad back so be a couple of weeks before we inspect fluid drive. Will let everyone know when I check it. A big Thanks to you and everyone who helped. Johnboy 

[MarcDeSoto]

When I opened up my fluid drive and smelled the fluid, it smelled like burnt oil.  I have a 48 DeSoto.  That is probably the original fluid put in at the factory.  I knew I had to change it by instinct.  Would you ignore burnt transmission fluid in your automatic transmission?  NO.  So I bought the Mobil One hydraulic oil suggested by James.