Checked fluid drive fluid level for first time on 48 DeSoto.

[MarcDeSoto]

I've owned my 48 DeSoto bus. coupe since 1980.  It has not been driven since then.  I read in the owner's manual that the fluid drive fluid level should be checked every 1000 miles.  Wow!  That seems like overkill.  Maybe they meant every 10K?  So, since I've never checked my fluid level in the fluid drive, I decided to check it today.  I turned the crankshaft over until the fill hole appeared in hole in the bell housing.  I put the 3/4" socket on the plug and opened it up.  As I pulled the plug away from the fluid drive, fluid started flowing out of it very quickly.  It kind of felt like a light oil, like 10w.  I put the plug back quickly to stop it from flowing out.  Although I know that it is supposed to be about level with the fill hole in that position. I smelled the oil on my fingers, and it smelt like burned rubber!  I don't know the history of the car.  Maybe a previous owner filled it too high in the past?  And where does the burned rubber smell come from?  Does fluid or oil rot with time?  Have any of you smelled that smell in your fluid drive unit?  

[Worden18]

I checked mine about 4 years ago.  It looked clean, didn't smell like anything.  The car had been driven less than 1,000 miles from 1973-2015.  After that is when I had the engine rebuilt and really started driving it. I might check it again here soon to reaffirm level and possible smells.  

[MarcDeSoto]

I just realized that the reason that the fluid started flowing out so fast might be because the car is jacked up pretty high right now for front end work.  So maybe it's not overfilled. But still don't know what the burned rubber smell is in the oil?  I do know that the last time I drove the car back in 1980, it drove fine down the highway for the 80 miles to my home in San Diego even though the engine was in very bad shape, broken rings, very low compression, etc.  It's rebuilt now, but hasn't run yet.  

[Dan Hiebert]

The oil used in fluid drives tends to last a very long time because it isn't exposed to much that wears it out, but, that burned rubber smell means that particular oil has been significantly overheated.  It is indeed a 10w oil, many threads herein on just what to use now.  Burnt ATF out of a bad AT smells just like burned rubber, some people replace the fluid drive oil with ATF.  Many "con" arguments against that, but that doesn't mean a PO of your car didn't do it.  There aren't really any friction parts in a FD unit, so I'd be concerned why the oil went bad, although overfilling the unit will put excess stress on its components, possibly overheating the fluid.  Definitely change the oil at a minimum, check it often thereafter once you get it on the road.

Edited December 25, 2020 by Dan Hiebert

[MarcDeSoto]

I read some research on Fluid Drive units and it said the fluid should be changed about every 7 years.  So I should replace mine.  I read that the closest thing to the original fluid is Mobil's DTE Hydraulic Oil ISO VG 32.  It's available online in one gallon containers for about $34.  Also O'Reilly's sells their own hydraulic oil that is ISO AW 32.  I don't know if this is the same thing though.  https://www.zoro.com/mobil-1-gal-hydraulic-oil-can-32-iso-viscosity-10-sae-101014/i/G3321692/

Edited December 24, 2020 by MarcDeSoto

[MarcDeSoto]

I wonder if this would be a good FD fluid:  I don't know what AW means though?  

 

https://www.oreillyauto.com/detail/b/o-reilly-oil-4527/chemicals---fluids-16461/maintenance-chemicals-16867/grease---lube-16582/hydraulic-fluid-17707/c48289420d31/o-reilly-aw-32-hydraulic-fluid-5-gallon/74309/4601121?q=hydraulic+fluid&pos=0

[Sniper]

AW means Anti Wear hydraulic fluid.

 

[Jeff I indu]

You can also buy the  DTE Hydraulic Oil ISO VG 32 at your local W.W. Grainger store. It should either be a stock item or one day to get it in store. Best price and no shipping assuming you have a grainger store near you

[Loren]

In my old machine shop we used the Mobil DTE products.

One of the machine manufacturers changed their spec for oil from a thicker product to a thiner saying that the thiner product had less heat build up.

They claimed the spindles would run 20 degrees cooler. In my not too scientific test I found that to be pretty close.

A fluid drive unit does not engage in torque multiplication so it doesn't generate the kind of heat a torque converter does.

All things considered I wonder how much heat an FD unit does generate in hard usage.

Certainly it would be more if you used a thicker oil medium. 

[MarcDeSoto]

Does anyone know the capacity of a FD unit?  Well if no one does, I will soon find out after draining my FD.  I found out that O'Reilly's Auto Parts sells a hydraulic oil, but it is described as a low to medium duty oil.  I think for a FD, I need a heavy duty oil.  

[MarcDeSoto]

Luckily, I found out there's a Grainger's store about 30 miles from me, so I will buy about a gallon of Mobil DTE Hydraulic Oil ISO VG 32 on Monday.  

Here is a description of the product.  It costs about $32 per gallon and the shipping cost is about $15.  

 

https://www.grainger.com/product/MOBIL-Mineral-Hydraulic-Oil-4ZF33  Correction!  This is the wrong oil to get!

Edited December 26, 2020 by MarcDeSoto

[MarcDeSoto]

I just found out that you can order the same Mobil product from Zoro and the shipping is just $5!  The shipping remains $5 for two gallons.  If you order three gallons, the shipping is free.  I was told by DodgeB4ya that he thinks the capacity of a FD is about 2 to 2 1/2 gallons.  

According to 48 New Yorker, this is the correct fluid to get.  See his post linked below.

 

https://www.zoro.com/mobil-5-gal-circulating-oil-pail-32-iso-viscosity-10-sae-104743/i/G0808272/?q=mobil light circulating oil

Edited December 26, 2020 by MarcDeSoto

[James_Douglas]

Marc, I assume you read my long tech note on the subject. James.

[MarcDeSoto]

Yes, James, that is where I got my information as you are the most authoritative person I've found on the subject, since you have done research on it.  

 

[MarcDeSoto]

I forgot about this post from 2019.  It's the best post on refilling your FD unit that I have ever seen.  He tells you the major mistake to avoid, as well as the capacity of the FD unit.  It's almost 2 gallons.