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The original Dexron fluid may very well have been a good substitute for Type A, but the elimination of additives based on whale oil "reshuffles the deck".

If you dig deep enough, you'll find reports, right here in these forums (maybe other, external sites, as well), from owners advising of moan/groan from the Direct Drive clutch with Dexron - including me. While that symptom typically points to a need for replacement of the DD clutch, many of those same owners have reported that drain and refill with Type F eliminated the noise.

Though that is purely anecdotal evidence, what's the problem if Type F buys an owner some additional time/miles on the DD clutch until a complete overhaul is truly needed?

Meanwhile, I've read explanation, online, that Dexron is "more slippery" than Type A, while Type F is "more sticky" than Type A. Seems to me that with all the factory documentation about premature failure of the high range clutch, you'd want the "more sticky" fluid.

As we do not have any scientific proof of the superiority of any type, nor any reports of damage/failure from any type, I'd agree that this anecdotal evidence favors Type F.

Sure. Or would favour any other type also for that matter.

Sure. Or would favour any other type also for that matter.

I can't say I agree with that statement; if you have a slipping or marginal direct drive clutch engagement, I think you'd be better served with the "sticky" stuff than the "slippery" stuff. Probably the reason why TrickShift has found so much favor with marginal Ultramatics.

Probably. I didn;t change to Dexron Mercom until after about 3k miles of driving with whatever trans fluid the previous owner used. He usualy followed Packard vendor recommendations. But i really don;t know what was in it from previous owner.
Clutch groan was always evident during the first 3k miles. after changing to Dex-merc the clutch groan went away after about 2k t0 3k miles of more driving. There is some very minor groan on rare occasions usualy in cold weather but even then not often.

If we look back several posts there is someone that indicated that Aller used the Dex-Merc too. hOwever, in that case we may not know what kind of modern materials Aller rebuilt the transmissions with in later years compatable with Dex-Merc or if he used Dex-MErc unconditionaly.

Edit: See post #4 above made by Jeff regarding Aller amd Dex-Merc.

WE are analyzing 50 year old transmissions. What are all of the possibilities???
1. An OEM unmolested trans.
2. A rebuilt trans using genuine PMCC parts or approved parts (probably rebuilt sometime in the 1958 to 1975 time range).
3. a rebuild using modern materials from a single source.
4. a rebuild using modern materials from a variety of sources or parts that fit from some other manufacturer of transmission.

So the type of fluid required mite depend on which catageory listed above decribes any selected trans.

when history of trans is unkown then what ATF is the best choice as a kind of 'one size fits all' fluid????

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Yes.

If the Ultra has OE or even factory-approved replacement linings, I'd lean toward the "more sticky" Type F - again, because of all the factory documentation regarding premature failure of the high range clutch.

The heavy-duty clutches that Studebaker announced for the Twin Ultramatic in SSB No. 344 shouldn't pose any problem WRT fluid - even if those parts are still available. The bulletin advised that shift quality was equal to the OE plates, but with longer service life.

IIRC, Kanter and others have promoted rebuild parts with modern friction materials that GM used - as solution to the problem of premature failure of those parts in the Ultra. While Dexron would be fully compatible in those cases, it is NOT required with Kanter's kits. See this post, which is also noted in my FAQ.

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I don't believe that there is a "one size fits all" fluid in this case.

If repair history is unknown or a mash-up of parts was used, then try Dexron first and give it a drive. If performance is unsatisfactory, refill with Type F. If that's unsatisfactory, then refill with Trickshift. While that might result in some money down the drain-pan, I see no other way.

I don't think this is as big an issue as using the wrong fluid type in a late-model vehicle.

Yet, after all this discussion, it looks like I need to revise my FAQ a bit.

Hi Folks:

I found a TSB for the Twin Ultramatic that specified switching to Dexron.

I assume the reason was that the friction modifier in Dexron would be beneficial in D range because L - H is a synchronous shift.

Thus, if you use D or manual L - H then I would use Dexron.

However, I never operate Ultramatic in anything other than High range.

Type F does not contain friction modifiers which is great for High range and Direct. However, if the purpose of the friction modifier is to prevent premature wear of high friction clutch facings by allowing slippage during boundary conditons (engagement period) then Dexron might be beneficial for all Ultramatics. That is, friction modifiers do not affect load bearing capacity, only shift quality.

Oils labelled as Type A are probably just AW32 hydraulic oil dyed red and repackaged as transmission oil for the purpose of selling excess stock.

Transmission "fluid" is just a colloqialism brought about by "Fluid Drive". It would be interesting to test 0w-20 motor oil as a transmission flush given it has detergents that might clear out stuck ball checks.

Although I've heard of a bulletin about the use of Dexron once before, I've never seen anything like that in all my years of collecting and studying supplemental, factory-issued, service info - and Studebaker continued to publish articles on Packard equipment, including the Ultramatic, into the early 1960s.

Can you provide a scan of that doucment for the PackardInfo archive?

I'm no engineer, but it seems to me that burned or prematurely worn-out linings are the result of load pickup and slippage issues. While Packard emphasized hydraulic and mechanical issues in their bulletins on high range clutch problems and Studebaker eventually came up with heavy-ducty plates for the Twin Ultra., that was at a time when there were no friction modifiers used in transmission fluid (oil).

As such, I feel that a "more sticky" fluid like Type F would be preferable in the Ultramatic, rather than a "more slippery" fluid like Dexron.

Can't remember where to look for it just the moment, but recall that the coefficient of friction of type F increases slightly as the relative motion of the parts ceases, and dexron does the opposite, slightly, for a softer shift. I always use type F.

Frankly, when the throtle linkage is adjusted properly I hardly ever have trouble with slipping of the high range clutches. The direct drive clutch is another matter and is a continual plague. Its problem is almost always rooted in wear of the bushings and subsequent loss of pressure to the clutch.

The high range clutches are fed by sealing rings in the 55-6 units so don't ususually suffer loss. Timing of the low-high shift is a bit of a problem on the 54-55 twins but can be brought up to snuff with a 56 valve body.

Whilst socking a new engine in my pickup I took the opportunity to freshen up my Ultramatic since it had gone 20k since its rebuild and was hanging in midair awaiting an engine. I always use drive range as I feel it saves strain on the troublesome reactor clutch. I was pleased to see that my Kanter supplied high clutch disks were EXACTLY as they were 20k before in spite of countless low high shifts. I put them back in. This in spite of my mod to the low-high shift valve spring (cut 5/16" off) to cause that shift to come about 4-5 mph sooner. With the direct shift valve shimmed .125", I get a really nice shift separation that makes the car more pleasant to drive, especially as it drops out of direct on slow uphill corners without the need to kickdown. I'm sure my main bearings appreciate that.