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Hydra-Matic Transmission

Started by Bruce Watson, June 08, 2010, 07:05:26 PM

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Bruce Watson

I have a 1948 series 61 Cadillac with a Hydra-Matic Transmission. I am wanting to change the fluid, but not sure what replacement fluid to use. All the manual says is genuine Cadillac Hydra-Matic Fluid!!!  I would appreciate if any one knows what to days equivilent product would be.

thank you

Bruce


Otto Skorzeny

#1
Virtually everyone with a Hydramatic uses Dexron/Mercon fluid.

Type A fluid is what the manufacturer recommends but it is extremely difficult to locate. I doubt your transmission has Type A fluid in it anyway but  you don't want to risk mixing them up so completely drain yours and refill it.

I've been driving regularly with Dexron in my '56 for 10 years with no trouble at all.

Ford automatics used Type A up to the mid 60s when Ford switched to Type F. Ford recommended Type F for transmissions made for Type A. My mom's '64 Galaxie works fine with Type F.

I know of at least one Hydramatic driver who uses the Type F without difficulty.
fward

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Mike Josephic CLC #3877

All of the Dexron fluids have been designed to be "backward compatable".  In other
words, you can buy the latest Dexron type fluid and it will work fine in your hydramatic
and will mix OK with the old fluid that you may have in there.

No need to look for the original type that your tranny used as it's no longer available.

Mike

1955 Cadillac Eldorado
1973 Cadillac Eldorado
1995 Cadillac Seville
2004 Escalade
1997 GMC Suburban 4X4, 454 engine, 3/4 ton
custom built by Santa Fe in Evansville, IN
2011 Buick Lucerne CX
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Past: VP International Affiliates, Museum Board Director, President / Director Pittsburgh Region

J. Gomez

Mike,

If you are referring to Type “A” ATF it’s still available by Warren Oil Comp. under the Gold, and Coastal brands. I had found these at the Dollar General stores; however they are becoming hard to find at these stores, I think hydraulic shops still carry Type “A”.

http://www.warrenunilube.com/

I do agree with you and Otto the best way is to go with Dexron, although Dexron maybe backwards compatible with older types, I  personally would drained the old fluid as much as possible including the torus and then refill with fresh ATF, instead of mixing them. Again this is just my personal preference.

I would also suggest removing the pan and clean the gunk from the bottom, and the filter just as an extra step to extend the life of the tranny.
J. Gomez
CLC #23082

Mike Josephic CLC #3877

Jose:

Good points.

I certainly agree with dropping the pan, cleaning out the crud and changing any filters
just as a matter of good practice.  One should try to get as much of the old fluid as
possible, however the amount you will get by dropping the pan is not all of
the fluid as you I'm sure are aware.

Mike
1955 Cadillac Eldorado
1973 Cadillac Eldorado
1995 Cadillac Seville
2004 Escalade
1997 GMC Suburban 4X4, 454 engine, 3/4 ton
custom built by Santa Fe in Evansville, IN
2011 Buick Lucerne CX
-------------------------------------
CLCMRC Museum Benefactor #38
Past: VP International Affiliates, Museum Board Director, President / Director Pittsburgh Region

Bob Schuman

Bruce,
I agree with the comments about using Dexron fluid in your old HydraMatic, and have a couple of additional comments. As I recall, the fluid coupling has TWO drain plugs 180 degrees apart. Take out one, then rotate the coupling a half turn and take out the second plug. This provides an air vent to permit all of the fluid to drain from the coupling. Draining the transmission pan is a separate step in fluid changing.

From work experience in the research labs of a major oil company in the late 1950's, this is what I recall about fluid types:
The frictional characteristics of Type F and Type A(later Dexron) were intentionally different. Ford transmissions needing Type F were designed for a fluid with more grip, and would slip when shifting if filled with Type A. GM transmissions were designed for Type A, and would shift very harshly if filled with the "grippier" Type F fluid. Maybe an old sloppy GM transmission can be improved by using Type F to firm up the shifting, but to me that is a "Band-Aid" solution, probably only temporary before an overhaul is needed.
Bob Schuman, CLC#254
Bob Schuman, CLC#254
2017 CT6-unsatisfactory (repurchased by GM)
2023 XT5

Bruce Watson

Thanks everyone for your information I will proceed to drain the Tranny & refill with the suggested fluid.

Thanks again

Bruce