What fluid does the transmission need?

Apr 6, 2007
120
Hunter Legend 37.5 Isla Saboga, Panama
I need to add some transmission fluid to the tranny, and it says on the fill cap to use Type A transmission fluid. Evidently, that is an old designation, and newer fluids are very confusing with their numerology.
Everything I read says not to mix different types of fluid, so I assume it would be best to drain all the old fluid out and replace it with new stuff, but what is the best stuff to use? The engine is the Yanmar 3JH2E.
 
Jun 15, 2012
694
BAVARIA C57 Greenport, NY
DEXTRON III is the replacement for Type A. If you want to stick to Type A it is available at Amazon. I would drain out all old oil and replace with Dextron III. Do not use synthetic!
 
May 24, 2004
7,129
CC 30 South Florida
Why no synthetic?
Although Synthetic oil would be the best logical product to use in a transmission as it is a clean and enclosed environment and with the oil being high temperature resistant it would last a lifetime but, many have experienced oil leaks after trying synthetic oil. Apparently old transmission seals and gaskets can be somewhat sensitive to changes in fluids. Having used synthetic oils in compressors and pumps successfully I also wonder about transmissions but I do not have to pee on the electric fence against the advice of those that may have before me. Regular oil or ATF does an adequate job and lasts a fair amount of time so why take a chance.
 
Mar 20, 2012
3,983
Cal 34-III, MacGregor 25 Salem, Oregon
EDIT... after re-reading the original post, I realize the poster is referring to type A fluid, not type F....
but the following still stands for those transmissions that calls for a type F fluid...

the original TYPE F trans fluid has NO other easy available options, unless you make up your own type F fluid....
ALL trans fluids EXCEPT type F has friction modifiers in them, and so it could make your transmission slip and overheat.....

I know this because I bought a boat with DEX III fluid in the trans which was suppose to have type F in it, and it overheated.
after a trans tear down and finding nothing wrong, I had to question the oil, since I KNOW the PO used dex III in it and had overheating issues for the last few years.
AND especially when the book says in capitol letters "USE ONLY TYPE F TRANSMISSION FLUID IN THIS TRANSMISSON"...... after calling the last 2 shops that sill work on these transmissions and talking to several people about it, I learned the information Im sharing here with you.
once I changed the oil to type F and running it a bit, the problems went away.... I changed it again a few engine hours later. and now after 300 engine hours, mostly at full throttle, there is no issues, whereas before the fix, we could hardly run at half throttle for 30mins without boiling the trans..... (oil would actually foam out the vent)

all im saying is... there is no trans fluid that will take the place of type F, when and if type F is actually needed for the particular application.
type F is still very much available, but not all auto parts store carry it, because most people think that dex 3,4,5 or 6 will take its place,... and so they just pour it in...

I dont know what trans you have, but I wouldnt take a chance... if it says used type F, get some type F fluid and use it.
 
Last edited:
Dec 25, 2000
5,702
Hunter Passage 42 Shelter Bay, WA
Hi Lee, your Yanmar engine, like ours, has an identification plate on the bell housing that designates the type of transmission lubricate for your boat. Follow what that plate states, not the fill cap. Our 4JH2-TE plate designates ATF. The PO used engine oil because they did not know any better. Usually it is between ATF or engine oil. Our 2GM stated engine oil. Check the plate before doing anything.
 

Gunni

.
Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
The techs at Mack Boring advised me to replace the Kanzaki ATF trans oil with Dex III. Been running it for years. No problemo.
 
Jun 15, 2012
694
BAVARIA C57 Greenport, NY
About synthetic, I have also read that it can react with bronze or brass parts that may be in your transmission.
 
Oct 28, 2013
129
Hunter Legend 35 Fairfield, CT
Ok, we have 3GM30F engine, and I just drained old transmission fluid and replaced it with Dextron IV synthetic... is that a bad idea? What should I replace it with? Thanks!
 
Oct 1, 2007
1,856
Boston Whaler Super Sport Pt. Judith
Although Synthetic oil would be the best logical product to use in a transmission as it is a clean and enclosed environment and with the oil being high temperature resistant it would last a lifetime but, many have experienced oil leaks after trying synthetic oil. Apparently old transmission seals and gaskets can be somewhat sensitive to changes in fluids. Having used synthetic oils in compressors and pumps successfully I also wonder about transmissions but I do not have to pee on the electric fence against the advice of those that may have before me. Regular oil or ATF does an adequate job and lasts a fair amount of time so why take a chance.
".........pee on the electric fence......" ???????
 

KD3PC

.
Sep 25, 2008
1,069
boatless rainbow Callao, VA
It's Dexron.....there is no T in the word. NO matter the suffix or number.
 
Apr 6, 2007
120
Hunter Legend 37.5 Isla Saboga, Panama
Many thanks for all the replies. I was able to find type A fluid here in Panama, but I will double check and make sure that's the correct stuff before I pour it in.