fluid drive fluid

[abs352]

I am the son of a proud owner of a 1948 New Yorker. What is the appropriate fluid for the torque converter, and how full should it be?

thanks, eric

[crazycars]

I have owned several of these cars and have followed the advice of respected collectors who instructed me to use 10W oil containing no additives in the torque converter (fluid coupling). I believe the trans takes 90W just like any standard shift of the period. I live near an oil distributor (US Oil) who sells this (10W) in 5 gallon pails and will mix any weight desired.

[Jon Robinson]

ABS:

The 10W motor oil that Crazycars recommends will work OK in the Fluid Drive unit, which is a fluid coupling, not a torque converter, really. I'm only telling you that because Chrysler did bring out a true torque converter on their V-8 cars in 1951, and knowing the difference can relieve confusion. Now, while the 10W motor oil works OK, it was really a Band-Aid that mechanics used in the 1960s just to get the cars back on the road. It's better to use tractor fluid, which by definition is TRULY without additives, and I have reason to suspect the tractor fluid has a higher specifice gravity, meaning that it "weighs more" under cetrifugal force just as it weighs more under gravitational force. The tractor fluid is much closer to the original fluid Chrysler sold for them, according to people who have compared the list of ingredients. You can get the tractor fluid at NAPA Auto Parts stores and farm equipment shops, but 10W oil will still get you through a pinch if you can't find the tractor fluid.

As for the transmission gearbox, DO NOT use the 90W oil! These transmissions did originally use 10W motor oil, but being that all of them are worn, they work beautifully on 30W NON-DETERGENT motor oil -- especially if you live in a hot climate as I do. I have about 230,000 miles on my 1950 DeSoto, and the transmission has never been touched.

You can drain the transmission and fill it up with kerocine and drive slowly around the block a couple of times, drain the kerocine out, and it'll clean it out nicely. No, it will not hurt anything!

Checking the fluid levels:

Fluid Drive: Lift up the carpeting on the passenger's side, and you'll see two inspection covers on the floorboard -- a big one on the side of the transmission hump for getting to the transmission's electrical components, and a smaller cover higher on the floorboard. Open the smaller one, remove the plug from the bell housing that you'll find, and turn the engine until you see the filler plug for the Fluid Drive. This inpection cover is placed so you're forced to fill the Fluid Drive unit to the right level. You can drain the Fluid Drive unit by removing the bottom half of the bell housing.

The transmission: There are two plugs on the side of the gearbox on the passenger's side. The drain plug is obvious, and the filler plug is about four inches above it.

A trick: Go to a well-stocked auto parts store and buy a quart bottle of Sta-Lube gear oil, and buy the pump that's made to fit the bottle. Dump the gear oil into another container for storage, clean the Sta-Lube bottle with gasoline, and what you'll be left with is a bottle with a really cool pump you can use for anything. You can fill the transmission and Fluid Drive unit with this setup really easily. I keep two of these bottles -- one with gear oil for the rear ends of both my cars, and one full of 30W for the DeSoto transmission.

JON

[Guest imported_BaronvonR]

Jon is Right......

When you do change the fluid in the fluid unit be sure to fill it to the top, it needs to be completely full.

I am one of those who still use the 10W in both transmission and Fluid unit, but I also live in a much colder climate. The 30W was reccommended for the hotter cilmates and was also suggested for the steering box as well.

BvR

[the3rsss]

I use type-f trans fluid in my fluid drive. I noticed a big improvement in power. Type f is cheap, easy to find, will not foam or breakdown, does not have any swelling agents that will ruin your sealsand It has the same viscocity as 10w oil. I have used it for about a year with good results. As far as the trans is concerned, the gyro-matic( or whatever chrysler calls it) calls for 10w while the standard calls for 90w.

[jipjobs]

I have used standard tractor oil in my fluid drive and it works great.

[ronm10]

your tractor fluid could be one of two wieghts. Some do not specify but some do. Those that do will have a letter and then a number. A number 32 is the equivalent of 10 wieght oil. A number 64 has the same viscosity as 20 wieght oil. Although I have never seen it in writing, in comparing the two numbers, any I have seen with no code seemed the same as 10 wieght oil. Thus number 32 hydrolic fluid (which is what tractor fluid is) and 10W non-detergent oil are equivalent as far a weight.

[bigdaddykarl]

Jon,

I seem to remember the kerosene trick referring to the fluid drive coupling in past posts, is this incorrect? I plan on changing out the fluid coupling fluid in my Windsor when I get home, (kind of difficult to work on a car while I'm in China) and was going to flush it with kerosene first. Should I avoid this? Is this method only for the gearbox?

I changed my gearbox fluid out (it was extremely low and causing the car to fall out of gear) with 30W ND oil, and now it is terrific. Living in Southern California makes the 30W just fine, as it rarely dips below 50F. In fact, I have noticed NO difference between the way it shifted before on the original fluid as now with the 30W. I was worried at first, as I couldn't find any retailer who carried 10W ND, and everyone looked at me funny when I requested it. But the 30W has been terrific.

-Karl

[Guest imported_BaronvonR]

What I have done with mine is to drain it and fill with ATF...drive around for a few minutes to really mix it up and redrain it completely. I have not used the kerocene method so cant comment on that, but found the ATF to do the job nicely. IF it is really dirty you can repeat the process, but drain thoroughly as you do not want to harm the seals with it being in there too long. I then filled it back up with the 10W and the car has run flawlessly. Everyone has their opinions on the fluid, so use what you feel is best for you. The 30W was recommended by Chrysler for the hotter climes, so you are correct in that for your transmission. You might also want to try it in the steering box as well, if I remember correctly.

BvR

[55PackardGuy]

You can also flush the Fluid Drive coupling using Baron's ATF method--but drain it completely afterward.

A note about transmissions: there's sometimes confusion over the "fluid" used in these '40s and '50s MOPAR trannys because there ARE different transmissions hooked up to Fluid Drive couplings. The early models with Fluid Drive, including the 46-47-48 Dodge used a standard 3-speed transmission that takes standard transmission "grease" such as 80-90 gear lube. Other models using the "semi-automatic" transmissions require the lighter oils mentioned. It's very important to check the shop manual for your particular vehicle to determine the weight of the TRANSMISSION oil/lube, but the FLUID DRIVE coupling ALWAYS takes a light non-detergent oil, such as one of the options mentioned. The manual will call for the "Special Fluid Drive Coupling Fluid" which has been unavailable for about 50 years.

I guess a good way to look at it is, unlike later "automatic transmissions" which were complete stand-alone units (sometimes referred to as "fluid drive") the MOPAR fluid drive setup uses a separate COUPLING that hooks up to whatever transmission they decided to put behind it. It's really just a buffer between the engine and the clutch. It facilitates the use of a "semi-automatic" transmission because it absorbs some of the mechanical force on the transmission, and allows the semi-auto to shift, BUT it wasn't always hooked up to a semi-auto, sometimes they used a standard 3-speed.

The Fluid Drive coupling is the only unit that needs special consideration and some decision-making about whether to go with non-detergent motor oil, tractor fluid (a special hydraulic fluid--my choice) or transmission fluid. If you go with tranny fluid in the Fluid Drive coupling, be aware that there have been problems reported--usually people saying that the additives or seal-softening components in some transmission fluids eat out the seal. There are others who say, "no problem," but I don't think it's worth the risk to ever use tranny fluid in the Fluid Drive coupling. Just my opinion.

I know I'm "preaching to the choir" for many who use this forum, but it seems this distinction between the transmission and the coupling is always an issue for anyone who first gets into one of these "fluid drive" cars. I hope I made it a little clearer for those who are still somewhat mystified. BTW, Chrysler Corp. never made a distinction about what <span style="font-style: italic">transmission</span> was being used when they stamped that <span style="font-style: italic">Fluid Drive</span> logo on the bumper. SO we can blame them for much of the confusion.

[Ed_D24]

Great points! In school I went through mechanical engineering and a key thing to think about is how the different components work (what they are doing) and what materials are used in their construction. This will help you understand what fluid should be used in each of the components.

As mentioned the point of the ?Fluid Drive? unit is to provide a coupling between the engine and the transmission. The point of the transmission is to provide variable gear ratios between the engine and the wheels (through another ratio the differential).

Also as mentioned, Chrysler (corp) chose a different approach than the other auto makers in that the ?fluid? coupling and the transmission were separated during the first few years of this type of technology. So, you will find a fluid drive between the engine and a ?standard? transmission in some Chrysler products while you will find it between the engine and a ?semi-automatic? transmission in other models or in other years.

So, to the details...

The fluid drive is a high speed fluid coupling (no physical/mechanical connection) and works with a fairly low viscosity fluid. It works through a ?high-speed? fluid property where the fluid acts as a ?solid? under certain conditions. Basically, the engine side in the unit spins and causes the fluid in the unit to stiffen and in essence become a ?solid? connection between it and the transmission side of the unit. This requires a fluid that will ?harden? under load yet will not ?foam up? when ?idle?. The ?tractor? fluid is appropriate in this case. It is a ?high-speed?, hydraulic fluid and works well in this application. It actually isn?t that hard to find in most areas. You just won?t find it at discount or most auto-parts stores. Look for a farm or industrial supply store, or ask a heavy equipment rental outlet (like US-Rents) for low viscosity hydraulic fluid. An example is the fluid used in the fluid drive used to drive lawn mowing units on large mowers that are used at places like golf courses. The fluid is a low-viscosity, non-foaming, non-detergent, hydraulic coupling fluid.

On the other hand, the transmission fluid to use really depends on what type of transmission is hooked up to the fluid drive. A manual transmission is shifted by YOU with the clutch disengaged (with or without a fluid drive). It operates with ZERO slippage and at relatively low speeds (in most cases). This calls for higher viscosity ?gear? oil. So a 70W-90W gear oil is normal. However, a semi-automatic will use a lower viscosity fluid like an ATF or a 10W oil.

[MilanBloom]

Where do I go to get a repair kit form my 1951 Fluid drive. I have contacted andy bernbaum and Roberts Motor Parts and they have no parts.

[Guest imported_BaronvonR]

That depends on what you need to repair...if its the seals then you need to look on partsvoice.com with the part numbers in hand. Thas what I did to find what I needed....if it is something else you need to tell us what it is.

BvR