Transmission fluid

[LaLeLu]

We are going to change to 30 wt in the transmission of our 1990 40 hp Yanmar. It presently has regular red tranmission fluid in it. Is there anything we need to do with regard to the switchover? I mean is it ok that there is going to be some residue transmission oil mixing in with the 30 wt?

[haffiman37]

Red transmission oil sounds to me like ATF 'A' oil, must have been there for quite some time! Be carefull mixing that type of oil with other types. Contact your Yanmar dealer and check to be sure if You do not have your instruction book for the engine. Mixing different oil types may cause clutch failures.

[LaLeLu]

Yanmar recommends using regular 30 wt engine oil in the tranny. I am not planning to "mix" the oils - rather to drain the tranny and refill with 30 wt. Of course there will be some residual tranny fluid. I am not sure if perhaps I should flush the tranny, or if a little residual tranny fluid matters at all.

[haffiman37]

To my knowledge there has never been produced a 'red' W30 oil which indicates that what you have is something else. The problem is not a few drops in the gearbox but what is left in your clutch package system. If not mistaken you have an multi disk clutch package and the disks are allready soaked with your old oil. If you mix ATF oil with W30 (engine oil) the risk is that your clutch system will start slipping when engaging into gear (delayed engagement). My recomendation is that you stay with the oil you have been using providing your gearbox works without problem.

[LaLeLu]

Perhaps my post was not clear. Presently we have regular red transmission oil in our transmission. We are planning to drain the transmission oil and replace with 30 wt engine oil.

[haffiman37]

Exactly what I presumed, except there is nothing called 'regular transmission oil'. What you have is an automatic transmission oil called ATF 'A'. I would not even be surprised if you find a sticker on the gearbox saying: use ATF 'A'. I am aware of that Yanmar today uses W30 (NOT multigrade) in their gearboxes, but they have made modifications on their clutch disks making them able to handle this oil. I expect your engine or at least the gear box to be a late 1980-production model.

[LaLeLu]

Thanks all for your input. Here's what another same-boat owner told me - in case anyone is contemplating the same thing I was...

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Only certain transmissions take the 30 wt engine oil. Most use “red” transmission fluid not engine oil. The two are not at all compatible. Ours is a 1997 Cone type transmission and it does use engine oil instead of transmission fluid. Yours apparently uses transmission fluid and should be replaced with transmission fluid. Different transmissions are used on the same model engines so you can’t assume someone with the same engine has the same transmission.

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Looks like my husband will be crawling around in the engine room on his belly this w/e to take a better look at the tranny...

[SailorMitch]

If the red ATF has been working fine since 1990 in the tranny, why change it now to 30 wt. motor oil? You're probably asking for trouble.

[kimberlite]

Hi,
we have a 2002 100 hp yanmar 4 cylinder engine the tranny
uses ATF and not oil.
they are not interchangible.
as i understand it yanmar uses 2 types of transmissions some use oil and others use ATF. i had the same engine with a different tranny in my last boat and it used oil.

get the make and model off the tranny and contact mack boring.
1-800-mackeng speak to the tranny shop.
they will tell you what you should use.
i would suspect you will need ATF and not OIL.
fair winds,
eric

[LaLeLu]

Originally Posted by SailorMitch

If the red ATF has been working fine since 1990 in the tranny, why change it now to 30 wt. motor oil? You're probably asking for trouble.

We would prefer to use 30 wt. b/c it is simpler to just have one oil aboard. Also the manual says that is what they rec. Our friends have a 50hp perkins that has ATF in the tranny now - but their mechanic told them to change it out and replace with 30 wt.