transmission oil change

Discussion in 'Diesel Engines' started by tropicalbuilder, Sep 29, 2011.

  1. tropicalbuilder
    Joined: Jun 2010
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    Location: costa rica

    tropicalbuilder Junior Member

    I everybody
    lately i got puzzled by two yanmar manual on the same motor ...
    one says to change transmission oil every 250 hours ...
    the other every 1000 ...
    what do you think??
  2. CDK
    Joined: Aug 2007
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    Location: Adriatic sea

    CDK retired engineer

    Such intervals are often ruled by commercial interests, especially if a specific brand of oil is recommended.
    There hardly is a technical reason to ever change transmission oil at all, just check the oil level regularly. Only if the oil has changed color or feels gritty between your fingers it is time to drain the oil and investigate the cause.
    One possible exception are transmissions using ATF. That is a hygroscopic fluid, collecting water through the vent on top of the transmission. If the engine is used infrequently and never reaches a decent operating temperature the gearbox fluid deteriorates and needs to be changed every few years.
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  3. whitepointer23

    whitepointer23 Previous Member

    i think it would mean 250 for engine , 1000 for trans.
  4. kenJ
    Joined: Jul 2005
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    Location: Williamsburg, VA

    kenJ Senior Member

    Depends on the type of transmission. If it is a Hurth or similiar brand that uses friction plates it should probably be changed every couple hundred hours or yearly if just weekend use.
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  5. Petros
    Joined: Oct 2007
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    Location: Arlington, WA-USA

    Petros Senior Member

    on auto engines, depending on type, they typically want oil changes in the equivalent of 100 to 200 hours of run time (5 to 10k miles). And for both manual (uses heavy gear oil) and Auto trans (Uses ATF) they want the equivalent of 600 to 750 hours (about 30k miles). Most people run them much longer without ill effect, and almost no one changed the rear diff oil even though that is recommended at the same interval.

    With the damp environment in most boat hulls it is difficult to imagine why they would use a longer change interval. Less dust and dirt in the air perhaps? Boats often sit for long periods of time without usage, so moister build-up would be a problem I would think.

    If this particular engine is known to have trouble because of infrequent oil changes than it might save you money to use the lower change interval. But as already noted, these intervals are mostly a way to get more money out of their customers, if the oil level is good and it is still "slippery", it is still good to use.

  6. michael pierzga
    Joined: Dec 2008
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    Location: spain

    michael pierzga Senior Member

    I change engine oil at 200 hrs and transmission oil yearly. I generate about 750 hrs per year on the powerplant. Do you need to change the transmission oil ? I have no idea...the oil I remove is always perfectly clear and the screen filter is always clean. The positive aspect of changing the gearbox oil is "general maintenance".. the oil change forces you to get down on your hands and knees for a half hour and observe the general rear engine condition. Chafed hydraulic hoses, weeping oil coolers, loose fasteners....become obviuos. This is the same reason why you change front end vee belts every 2 years....inspection. Oil is it.
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