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M5 Fluid Drive - coupling capacity and observations


48 New Yorker

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Just got finished replacing the oil in my M5 Fluid Drive…after 12 years.  Unfortunately, when I first got my Chrysler New Yorker,  I installed the “slightly” wrong oil;  “Mobil DTE 24 Hydraulic …. should have been “Mobil DTE Oil Light Circulating Oil” - manuf. part number 104743.  

Mobil’s naming scheme is confusing,  however my mistake allowed me to compare both blends.  The DTE 24 has additional additives, but IMO, was more "slippery" and didn’t accelerate the car as quickly as the DTE Oil Light Circulating 104743 --  while not fast, I’d say that it’s much more “sprightly”.  The only downside is that the DTE Oil Light comes only in 5 gallon pails…. and it ain’t cheap….I found it locally for about $100…well, at least I’ve got a 30 year supply….

 

A few observations:  

-  the fluid coupling of an M5 takes exactly 25.5 cups or 6.375 quarts. 

-  instead of using a rag to keep the plug from falling into the bell housing,  I used a thin piece of aluminum sheet to make a tube that fit in the fill hole.... left more room for the socket wrench.

- make sure the car is level.  On my first refill years ago, didn’t realize the gentle slope of my street… under-filled the coupling by 3 cups.  This time I used a level and jacked the back end.

-  a DIY slow drip system is a lot less fatiguing, allows you to walk away while it’s filling…see photos.

-  Jame Douglas deserves a round of applause for his research into the correct oil for our Fluid Drives, he got it right.

 

David in Santa Cruz

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Thanks for this info.  I am going to be refilling my 48 DeSoto fluid drive soon also.  Somewhere in the past I heard you could use automatic transmission fluid.  Looks like it's available by the quart and gallon too.

 

https://www.ebay.com/itm/Mobil-DTE24-Light-Hydraulic-oil-1-Gallon-128-oz/302112065835?hash=item465748492b:g:IqsAAOSw1KxXMhcu

Edited by MarcDeSoto
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Marc: The Mobil DTE 24 in your ebay post is not what you want.  While it won't damage anything, you won't the the correct performance out of it.  Its additives make it a bit too slippery; which makes the tranny feel as if it is slipping/sluggish.  

 

Chrysler1941: Both Mobil DTE24 and the correct Mobile DTE Oil Light Circulating oil are ISO32.

 

The easiest way to get the correct Mobile oil is to ask for it by the manufacture's model number which is  Mfr #: 104743

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My d-24 is nowhere near a hot rod with my standard 3 speed in it, but at least I no longer have any too foamy too slippery where do I find the right oil boy is this sluggish issues since I ditched my fluid drive. Being able to drive it without the clutch all the time wasn't enough to offset the snails pace for me.

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The M5 is not as much of a slug as some think it to be.  I think the problem is that few people really know what to expect regarding acceleration because they’ve never used the correct fluid…. it’s a case of “I’ll put in whatever oil I found and now the car moves and shifts….problem solved”, and the result is how they think it’s supposed to perform.   Wrong.

 

My reasoning:  Let’s say that the original fluid will last about 10 years before it starts to deteriorate (well beyond the length of time Chrysler engineers felt/hoped an owner would hold on to their car).  Sooo, in my case (’48 New Yorker) my fluid would have been due for replacement around 1958…. Since they stopped making the stuff in the mid 50’s, everyone has been using something yellow or red that would pour…..ATF, 10w oil, Tractor Fluid, Vitalis, oil&vinegar etc. 

 

I just compared two very similar oils in everyday driving and one gave much better acceleration than the other.  The DTE 24 with a few additional additives was inferior to the DTE Light Circulating Oil.  

 

My point is this:

   Very minor differences in oil formulation can make a big difference in how an M5 tranny car accelerates and preforms...if you've never installed the right stuff, how would you know how it's supposed to perform? 

 

My 48 now keeps up with around town traffic easily given it’s weight and horsepower…135hp/≈3900 lbs.  If you decide to try Mobil DTE light circulating oil, use the product number to prevent confusion:  Mfr part#. 104743

 

As to the current uses/specs of Mobil DTE Light Circulating, see the product data sheets attached below. 

Mobil Circulating oil vs Hyfraulic oil.jpg

DTE Light, Medium, Heavy Medium & Heavy pds.pdf

Edited by 48 New Yorker
spelling typo
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MarcDesoto:

I would try a local "industrial oil distributor" or on line Granger or Zoro, see links below, however my best price was from a local place called Toro Watsonville CA.  ≈$100/5 gal pail.

 

https://www.toropetroleum.com/

 

https://www.grainger.com/product/MOBIL-Mineral-Circulating-Oil-4ZF36

 

https://www.zoro.com/mobil-mobil-dte-light-iso-32-5-gal-104743/i/G0808272/?gclid=CjwKCAjw7O_pBRA3EiwA_lmtfhAEUUY-lyh571MNrjK5ofbfSxnrtkI-9QW6xqePSIATZLI2PfoPfhoCiAQQAvD_BwE&gclsrc=aw.ds

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If you really want to see how well a Fluid Drive performs against a stick, view the video below from the :43 sec. mark.

 

I’m absolutely, positively sure they didn’t speed up the film for that sequence ….nope….nope….nope….

 

 

 

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I've been around fluid drive couplings and the many different transmissions that are associated with it for many years........ and none are as speedy as a regular standard transmission, but at least none of them are a Dynaflow.....lol. I hope you guys enjoy your fluid drive couplings as Ma Mopar intended...they make for a very stately cruiser and certainly would not wear out my leg as much on long trips, I'm headed for a 904 or a 518 somewhere in the near future.

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Hey.....I've got two Dynaflows both are fast ...............................................leakers.

Edited by 48 New Yorker
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