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ZF350A Transmission small leak

Discussion in 'Technical Discussion' started by CSkipR, Apr 9, 2011.

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  1. CSkipR

    CSkipR Member

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    From some of you experienced captains can you provide any insight to where one of my transmissions most likely would be leaking. Its a small leak but I'm sure it will grow in time and headed to the Bahamas in a month. I run Mobil 1Delvac 5-40w in them same oil as engines.
  2. Capt J

    Capt J Senior Member

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    Usually they'll leak out of either the front or rear seal. Clean the transmission well with a degreaser and the bilge underneath it, and lay diapers underneath it, then keep an eye on where the diaper is getting soiled or before cleaning it use a mirror and your hand and try to feel or see where there is residue. How much oil is leaking?
  3. CSkipR

    CSkipR Member

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    Capt J,
    The leak is pretty minimum maybe 1/4 pint or less everytime I run the boat for a few hours but with a trip to the Bahamas I prefer to try and fix it. Can the seals be replaced without pulling the trans?
  4. K1W1

    K1W1 Senior Member

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    Hi,

    Can you see any oil in the bilge or does it just vanish from the dipstick?
  5. CSkipR

    CSkipR Member

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    I see it in the bilge below the port trans and into then into the area between the two engines. I have a diaper under the trans just haven't gotten down there close enough to see where the leak is. Will have to see if its visible using a mirror.
  6. Capt J

    Capt J Senior Member

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    The rear lip seal can usually be done with the transmission in place and just dropping the shaft. However the front one, requires splitting the transmission from the motor in most all cases. a 1/4 pint is actually becoming a good size leak for a tranny. Does the transmission have an external filter that could be leaking?
  7. CSkipR

    CSkipR Member

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    I don't believe it has an external filter at least I've never seen it. Will confirm with the manual.
  8. Capt Fred

    Capt Fred Senior Member

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    Something to check, my ZF 220, run straight 30w, make sure your's is OK with 5-xxw.
  9. CSkipR

    CSkipR Member

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    Thanks, you are correct that is what they recommend in the manual as I just read it again. The engines and trans have had Mobil 1 Delvac 5-40w before I owned it 4 years ago. Hopefully no damage. Could the lower wt oil potentially cause a leak? Another question can I check the filter screen without removing the oil in the ZF350A?
    Thanks
  10. K1W1

    K1W1 Senior Member

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    Hi,

    You will hopefully be lucky, I was involved in a vesel once with ZF BW 755 Gearboxes that were supposed to run straight 30 but had for the preceding 3 yrs been run on a steady diet of Shell Omala 150 which is a heavy gear oil.

    It was caused some amazement to the bridge team when the correct grade of oil had been flushed through the system a couple of times that the low clutch oil pressure alarms that had dogged the boat since new when manoeuvring vanished by themselves.

    From memory there was about 1100 hrs on the engines when the mistake was noticed. Up to that stage all Oil Samples had come back as being fit for further use. As the Lab had been unable to notice the wrong oil was used I was not sure if this was an honest interpretation or not so the vessel changed analysis services and chief engineers at about the same time.
  11. Capt J

    Capt J Senior Member

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    It is possible that the wrong oil is causing the leak.

    If it is the ZF style I am thinking of with the scraper, and the scraper handle looks almost like a battery terminal. The entire drum comes out with 3 or 4 bolts (scraper handle and all), you then take it off the boat and clean it with brake fluid, and you need a new paper gasket to put it back ($5 gasket). Be careful not to damage this as the filter assembly is $1600 from ZF. There is also a bolt near the scraper handle that you take out and after scraping it, you can drain out the scrapings. CALL ZF in Miami, they are VERY good about giving advice on how to maintain their transmissions and will walk you through every single step.