'48 Fluiddrive fluid

Subject says it all. What fluid should I be using to replace the fluid in my 1948 Chrysler Windsor FluidDrive? It has the straight 6, model C38.

I have 2 Chrysler products with the fluid torque and in both I use 10W non detergent oil. I purchased it from my local NAPA. This is what my manuals state goes in there and I have had no problem with either car since changing the fluid. Be SURE it is this oil as some of the additives in other products can destroy your seals.

Baron,

Thanks for the great tip! I'm new to this forum and working on getting a '47 Dodge 6 with Fluid Drive out of the field and into a workplace before winter. I don't have the shop manual yet--just ordered one from Faxon.

Meanwhile, I want to get going on it and am wondering about changing the trans oil before starting the car. It has been sitting a while. Is there any danger to the transmission if the car is started with old oil or low oil? How do I check and change it?

Right now, the car is up on blocks, and I was planning to try putting it in gear once I get it started to see if everything turns, but I hesitate to do so before knowing more about the transmission.

Any help would be appreciated.

BTW what years and models are your two Chrysler Products with Fluid Drive?

Hi,

There is no danger in starting the car to see if all is well when it is on blocks. What you need to realize is that the transmission and the fluid coupling are two different items. The transmission and coupling both take 10W oil. If you drive the car a short diatance with low trans oil it wont harm it, but not recommended for anything more as you may damage the bearings. The filler and drain plug are on the drivers side of the transmission and should be changed even if it is full once you get it into a dry place.

The fluid drive is forward of the transmission and also takes 10W oil. If it is low on oil it will still "drive" the car, but will feel like the clutch is slipping. This is what was wrong with my '51. The fluid was low and it barely made it up hills....feeling like the clutch was slipping badly. To change this is a bit more involved. You have to lift up the carpet on the passenger side front and there are two access plates on the engine hump. the one closest to the engine is the one you open to gain access to the fluid drive. You must then rotate the unit until you see the filler plug....remove the plug, being careful not to drop it....and rotate the unit to the 6 o'clock position. This will allow the oil to drain....there is no real place for it to run so be sure you have a large pan to collect the oil. Then re-rotate the unit to the 12 o'clock position and fill to the top with the 10W. Next you check for leaks, because if it was low there will be seal leaks. If not you are good to go. Mine remained at half full, and all the rest leaked out rather quickly....so I had to remove the transmission and fluid drive unit and replace the seals, and while I was at it I replaced the clutch disc.

I hope this helps you...be sure to get the shop manual for the car as well as a parts book so you can search for the parts you need by number. I found most of the needed parts on www.partsvoice.com

My cars are a 1951 De Soto Custom 4Dr, and a 1950 Chrysler Imperial Deluxe 6 passenger.

Thanks Baron!

This is indeed essential information. I haven't gotten the shop manual yet, but I doubt it will have any better instructions for checking oil levels. Thanks also for the parts tip. I'm sure I'll need it.

I'll be visiting "Jack" the '47 Dodge this week yet. Sorry, couldn't attach a photo--the file's too big. Well, it IS a big car...

BTW, is either or both your Chrysler and DeSoto an 8 cylinder?

Thanks again for the info <img src="http://www.aaca.org/ubbthreads/images/graemlins/smile.gif" alt="" />

My De Soto is the 116 hp 6 cyl and my Imperial has the last of the 135 hp straight 8's (Chrysler went to the Hemi's in 1951). It is a more unusual engine in that it has hydraulic lifters.

Here's another opinion on this topic: Chrysler literature indicates that non-detergent 10-W motor oil should be used in the GEARBOX (accessible from under the car). However, the fluid drive unit, (accessible from inside the car through a panel in the right-side of the tranny-hump, should be filled with "Mopar Fluid Drive Fluid." I believe this fluid is nothing more than ordinary, clear mineral oil..... I've also heard that Chevron makes a similar product called something like "Torque-Coupling Fluid," and that some tractor dealers sell a product for use in fluid couplings on some-make tractors. Also heard that Ford Type "F" automatic transmission fluid works, as well. Motor oil is supposedly too "slippery" for this application. It may work, but it's possible you'd be losing some traction! I suspect Chrysler had a reason for not dumping motor oil down that hole..........

I have a NOS unopened can of the MoPar fluid drive fluid and upon inspection find that it is indeed 10W oil. There are some in other parts of the country...hotter climes, like the southwest deserts....that use 30W oil for the trans and regular trans fluid in the coupling, and seem to do fine with the heavier oil. The tractor fluids contain agents that will destroy your seals and I would strongly urge you NOT to use that. I have been running 10W in both of my cars now for over a year with no trouble/slippage whatever. I drove my De Soto to Ohio this year...500+ miles, and no trouble at all. It is your decision what to use....you can always check what comes out of the fluid coupling when you drain it to see what was in there, my mechanic told me it was 10W in mine when he changed it.

Just got the Shop Manual re-print from Faxon. They were fast and very reasonable, I thought--$20 plus $4.95 shipping. Took about 10 days, although I sent them a check so it could've been faster. They no longer have a web site of their own, but sell over e-bay. You can make a "bid" starting at a penny below the asking price! So, the bidding process is not really in effect.

Anyway, the book does not give a capacity for the fluid drive! It just says fill it up to the hole with MOPAR Fluid Drive Fluid. I doubt they still make that. It calls for changing the fluid drive every 10,000 miles.

Baron, do you know about how much 10W it holds? I don't want to be short or end up with a ton left over!

Although the extra could go in the engine, according to the book, which calls for 20 or 20W above 32 degrees and 10-W under 32. Get this below -10, it calls for dillution with 10% colorless refined Kerosene! Those were the days.

What oil do you use? I've heard that oils with "diesel" ratings have high film strength that works well in older engines. I'm thinking 10W-30 would be about right.

The TRANSMISSION however, calls for SAE 90 gear lube. Capacity is given at 2 3/4 pints. Below 10 degrees F it calls for SAE 80. Sounds like good old 80-90 gear lube would be the ticket.

BTW, transmission fluid is very high detergent as well as being light. I agree that you would be just asking for leaks and eaten seals if you used it in the fluid coupling.

Cheers!

It is interesting that the manual calls for gearlube 90 in the transmission....that belongs in the steering box and rear end only. My cars have a tag on the side of the transmission thats says 10W oil only. Please be sure you did not mis-read the manual, because it really is 10W that goes into the transmission.

As far as amounts of oil in the fluid coupling, if i remember it was around 7 or 8 quarts. I just bought a case of the oil....12 quarts...and keep the rest for topping off the transmission if I need to. I do not think that you really need to change the oil every 10K miles....for starters, unless this car is a daily driver, you wont be putting on the miles. When I had the oil changed in my Imperial the mechanic told me that it looked like the original stuff....who knows ...it was black....I am not planning on changing mine for the next several years at the very least.

I run straight 30W in both of my cars....I tried using the multi viscosity oils and found I burned oil. I have been told that if you are planning on rebuilding the engine then you can use the newer oils as the engine will be tight, but if not then use the 30W non-detergent. If it is a very clean engine then the 30W detergent should be fine. I change oil and filter once a season regardless of the miles I put on. The 20W oil is if you run the car in the winter, which I never do....I dont like rust:)

Enjoy your car, if you take care of it, it will give you years of motoring pleasure. On a side note I find that the 6 cyl motors from the 40's do best at 55-65, if you plan on doing interstate driving. After 65 the engine screams...it is a low rpm high torque engine and has a soft crank...too much of 65+ can produce a knock...the only way to safely increase the speed is to add an overdrive or change the gear ratio in the rear end.

Baron,

Roger on that speed. The final drive figures I've seen are around 4:1. Considering that they basically had a torque converter up front, I'd think an overdrive would have been a logical choice, but maybe they thought it to be an unnecessary expense.

On the transmission, I double-checked and it absolutely says SAE 90 for temps above 10F and SAE 80 for temps below 10F. This is a direct reprint of the original shop manual, so it's perhaps an original mistake! I would definitely go by whatever it says on the transmission tag. However, if there's no tag, I'm leaning toward going with the heavier lube. What can it hurt, besides taking more power to turn the trans? Also, I'm wondering if the Dodge and Plymouth had a different trans than the Chrysler and Desoto? Or perhaps they changed after the '48 models? I believe the "D-24" model designation was for '46-'47-'48.

This question won't be an issue until I get the trans lube changed, which as you say may never have been done, so there's not a huge hurry now. I'll check it and top off with some 30W if needed now. The stuff that's in there is probably plenty thick <img src="http://www.aaca.org/ubbthreads/images/graemlins/wink.gif" alt="" />.

As far as engine oil, I can understand a multi-weight tending to burn in an older engine, but doesn't a detergent oil help keep the crud cleaned out?

Whatever I do, I'm keeping records of all your helpful hints and referring to them as I go. <img src="http://www.aaca.org/ubbthreads/images/graemlins/smile.gif" alt="" />

I checked my copy of the 1941-48 Dodge Shop Manual, and it does state to use SAE 90 fluid gear lubricant for temps above -10 F and SAE 80 below -10 F.

The transmission on the 1948 Dodge is the normal 3-speed manual Mopar transmission - Dodge did not get the 4-speed semi-automatic until 1949.

The 1941-48 Chrysler Shop Manual also lists the same SAE 90 / SAE 80 requirements for the 3-speed manual transmission, as does the 1946-54 Plymouth Shop Manual.

However, the 1949 DeSoto Shop Manual advises to use SAE 10-W engine oil in the 3-speed manual transmission.

So something changed in 1949 for cars using Fluid Drive along with the 3-speed manual transmission.

Bill

Vancouver, BC

Here's what Greg G from the P15/D24 forum says on this matter.

"This seems to be one of those "here we go again" items brought about by the Fluid Drive label being applied to several different drive system by our friends at MOPAR corporate headquarters. You mention yours is a Dodge. Thie was the simplest form of fluid drive, whereby the standard three speed tasnmission and clutch are driven by a fluid coupling instead a fly directly connected to the driveshaft. What Pat is refering to is the M style semi automatic transmisions used in Chryslers and Desotos. Your Dodge has what is basically a oversized washingmachine hydralic clutch bolted to the crankshaft, and the flywheel bolted to it, then a standard three speed seperated from it by a standard clutch set up. No torque multiplication going on just an impeller driving a stator through a fluid medium ( the tractor hydralic fluid mentioned in another post) The advantage here being that for city driving you can choose t leave your car in top gear and drive, albiet sedately, by using the gas pedal and brake just as would an automatic, and the fluid provides the slippage and gradual engagement to allow this through the coupling instead of slipping the clutch. So see a simple demonstration of the principle, set up two electric fans facing one another, the air between them being the fluid. Turn on one fan at low speed idle, and you can either drive the undriven on at nearly the same speed, or stop it easily with your finger. If you then let it go and increase the speed of the powered fan, the unpowered one will follow along at about the same speed less any fritional losses, connect your clutch and tranny to the driven fan, and you have the Dodge fluid drive system. But enough of this long winded post...

Hydralic fluid suitable for commerial or agricultural hydraulic systems, this would be for pump and ram things like bucket loaders, trench diggers etc. for the Hydraulic coupling, and 80 or 90 weight gear oil ( the stinky stuff) for the tranny and differential. If and when you you decide to do anything, you should drain the coupling completely and completely refill with your new choice."

Reg,

I kinda thought something must've been different in the "newer" trannys. They talk about an electric "kickdown" switch and other enhancements on them. Do you know when the basic fluid drive coupling was introduced? I got an e-mail regarding this subject from a fellow who had a '42 Chrysler Royal with it. The Chrysler club told him to put in Dexron III auto trans fluid, which they said was basically 10W oil. He said he's had it in for 7 years with no problems. He was getting a little worried reading the cautions against using transmission fluid, and was thinking about changing it out.

When you say hydraulic fluid, do you have a particular kind in mind? I was almost settled on going with non-detergent 10W to stay away from any additives that might eat the seals. Are there properties of hydraulic fluid that make it superior in this application?

Thanks for the inside scoop on how the early fluid coupling worked. It's different from a torque converter setup, isn't it?

I suppose I can go look on P15-D24 for another answer to this--probably from Greg, eh? <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" />

Poured 10W into the filler of my M6 fluid coupling (TipToe Shift) on my '51 Desoto 6-cyl. sedan, and it ran right out the bottom, via the hole -- which appears to be square in cross-section -- shown, located at the bottom of the bell housing. Likely scraped off the drain bolt or whatever in driving, or maybe it was never re-installed after the last draining (the car was just delivered a week ago).

Any idea as to part # of this bottom bolt/seal/plug, or where I can buy one?

Robert

OH Gawd....Here we go again.!

The Fluid Drive  "Whack-A-Mole" help game. 

You poured oil directly into the Fluid Drive/clutch bell housing.

You need to rotate the fluid drive unit till the fill plug lines up with the 3" fill hole in the bell housing -remove the FD filler plug and check the level

.Don't change the fluid! Leave it alone if full.... I'm not going any further with this as whats right fights will ensue!

If you found the removable plate in the driveshaft tunnel below the dash, and the round hole in the bellhousing under it, now you need to "bump" the starter until the fill plug comes into view. Disconnect the coil wire so the engine won't start. Remove the plug with a socket wrench but stuff a rag around the hole first. So you can't drop the plug down in the bellhousing.

A lot of us use Tractor fluid, TDH type, ISO22 or ISO32 grade. You can get it at auto parts stores and farm supply stores, some Walmarts and Canadian Tire stores have it. TDH stands for transmission, differential and hydraulic oil, It is good for the Fluid Drive unit and the M6 transmission too.