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Correct lubricant for Chrysler Vacamatic S-A Transmission

Rich C.

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RE: My 1942 Chrysler Royal 6 Cyl./Vacamatic/FluidDrive/75K miles

About to put in a new clutch in Betsy. Also bought the transmission extension housing seal (Timken #8160S) since I notice leaking at the drive shaft.  Expect I will have to top off the tranny oil.  Past conversations says 10W weight in the Vacamatic transmission.  That would be Non-Detergent Single Weight.  In Florida I presume 30W would be a better choice.  However all I can find in ND SAE30 weight are products like Valvoline #822382 "Non-Detergent Oil SAE30/ISO100".  A call to their hot-line in Kentucky and their product safety data sheet reveals this in Mineral Oil not Petroleum based.  NAPA, PureGuard and others are the same. Questions:

A- Is there a petroleum based 30W ND oil out there?  I've tried Farm/Tractor Suppy stores. Those say Mineral Oil right on the label.

B- Mixing 80 year old Petroleum Oil and Mineral Oil is NOT a good idea.  Right?

C- A few ounces of modern Detergent-SAE30 mixed with the original 10W would not hurt.  Right or wrong?


Also any tips on pulling the tranny down and changing the clutch on this baby is much appreciated.  My first attempt.


TIA, Rich C., Florida

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There have been a number of prior threads on this.  10W is available.  I think I have a case of it.  If you can not find it, I will be happy to sell you some of mine for what I paid for it.  Will have to go back and look.  

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10W and 30W is not the same thing.  I and others recommend TDH Tractor Fluid ISO32 or ISO22 grade for these transmissions and Fluid Drive units. They are separate but both take the same fluid. TDH stands for transmission differential and hydraulic fluid. You can get it at Walmart, auto parts stores and farm supply stores.

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Sorry I mis-typed. No such thing as 30W.  SAE30 is intended for summer use only.  10W is designated for Winter use.

Since we have no hard winters in Florida (seldom gets below 40°F where I am) and the typical garage temperature when I start her is 85°F, I'm thinking I don't need SAE10W.

I did read about TDH ISO32 Hydraulic Fluid for the Fluid Drive.  Not concerned about that.  It comes in 5 gallon containers, I need about 5 ounces to maybe top off the tranny.

All Hydraulic Fluid is Mineral Oil.

So (in quart size):

Valoline SAE30 Motor Oil (product #79798 $8) is desctibed as "Conventional Motor Oil" with High Detergent additives.

Valvoline SAE30/ISO100 "Non-Detergent Oil" (product #822382 $8) is described as Mineral Oil with no detergent additives.

So they are not the same oil, one with cleaning additives and one without.

Valvoline does not make an SAE10W "straight weight" HD or ND formulation.  They are all multi-viscosity blends like 10W-30 HD for cold climates.

Any time I find an SAE10W Non-Detergent off-brand - it's a Mineral Oil based product and usually called Fluid or Lubricant.

Don't think they had mineral based oils in 1942 - but I could be very wrong.

I see a lot written about "don't mix hydraulic fluid with motor oil".  (I have some screen captures.)


Back to my original questions: A, B & C.


I do not want to open and flush the tranny, clean out all the old oil and refill it with 44 ounces of fresh TDH hydraulic fluid.  (Although Betsy may like that!)

The Fluid Drive is not leaking and I'm going to leave that alone too.


I certainly appreciate your replies guys (or gals!!!).

Rich in Florida.

Edited by Rich C. (see edit history)
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My TDH fluid came from Canadian Tire, it was around $10 for a gallon or about the same as 2 quarts of motor oil. This is a lifetime supply. I bought it about 10 years ago no doubt it is more expensive now. But you should be able to find it in 1 gallon size somewhere.

Chrysler manuals do not give different recommendations for hot or cold weather, it's 10W across the board. They do recommend heavier oil in the motor in summer but not the transmission. The fluid drive works better the thinner the oil.



Edited by Rusty_OToole (see edit history)
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The transmission takes 10W non detergent oil.  The Fluid Drive does NOT take the same oil, although many have put 10W motor oil in the FD.  The FD takes a very special  Mobil Light Circulating hydraulic oil that prevents cavatation.  It is sold by Grainger and Amazon:  https://www.amazon.com/Mobil-DTE-Light-ISO-gal/dp/B07CSLKT1J/ref=sr_1_45?crid=14IIL4SIF3KVT&keywords=mobil+light+circulating+oil&qid=1660542104&sprefix=mobil+light+circulating+oil+%2Caps%2C111&sr=8-45

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On 8/11/2022 at 9:42 PM, Akstraw said:

So what is it that you are looking for, the correct oil, or permission to use the wrong oil?


This Lubriplate is MINERAL OIL.  Not the same as what Chrysler put in their trannies in the 40s.  (Detergent additives were added in the mid-50s and you need an oil filtering system, like in the engines to get the benefits.)


QUOTE: "The transmission takes 10W non detergent oil.  The Fluid Drive does NOT take the same oil..."

and I agree.


I don't think Mineral Oil mixes with vintage petroleum Motor Oil in these old trannies.


Rich C.

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Group I and II petroleum oils are referred to as "mineral oils" whereas Groups III and V are referred to as "Synthetic Oils".   It may incorrect to conclude that a motor oil product identified as "mineral oil" is not petroleum-derived.  Check out this definition:


min·er·al oil
/ˈmin(ə)rəl oil/
  1. a distillation product of petroleum, especially one used as a lubricant, moisturizer, or laxative.
    "lipstick may contain mineral oil and artificial colors"
Also this from the Castrol website:
There are so many motor oils out there, which oil type is right for your vehicle? Well, there are three basic types: mineral, semi synthetic blend and full synthetic. Mineral oils are the least refined of the three, which means they cost less, but also provide less protection, performance and economy than the other options. Part synthetic motor oils are a blend of mineral oil and synthetic oil, to give added performance, but still at a lower cost than full synthetic motor oils. Full synthetics are the most expensive motor oils as they are highly refined, but offer the best protection and economy to absolutely every vehicle.
Edited by Akstraw
additional info (see edit history)
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