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Thread: Gearbox breather

  1. #1
    Member AKAMick's Avatar
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    Gearbox breather

    I removed the breather (vent) on the gearbox of my 70 T, mag case to clean it, I never paid attention to its orientation and now understand it is aligned in a particular way, which way does it look? thanks,

  2. #2
    Senior Member
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    Forward I believe.
    Porsche Historian, contact for Kardex & CoA-type Reports
    Addicted since 1975, ESR mbr# 2200 to 2024 03
    Researching Paint codes and Engine Build numbers

  3. #3
    Quote Originally Posted by AKAMick View Post
    I never paid attention to its orientation and now understand it is aligned in a particular way...
    Breathers on pre-915 transmissions are installed with the vent hole at a 45° angle from forward.

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    Jon B.
    Vista, CA

  4. #4
    Member AKAMick's Avatar
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    Thanks! that is good information, wonder why it is like that, must be some reason for it?. now i can get it back in correctly, thank you.

  5. #5
    Quote Originally Posted by AKAMick View Post
    wonder why it is like that, must be some reason for it?
    To prevent your garage floor, driveway and local roads from being lubricated.

    Jon B.
    Vista, CA

  6. #6
    Member AKAMick's Avatar
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    Quote Originally Posted by Jon B View Post
    To prevent your garage floor, driveway and local roads from being lubricated.

    Jon B.
    Vista, CA
    How does the position of the vent cause the lubricant to expel, and from what would it leave from?

  7. #7
    Quote Originally Posted by AKAMick View Post
    How does the position of the vent cause the lubricant to expel, and from what would it leave from?
    I'll assume that Porsche analyzed the fluid dynamics and flow paths of the transmission oil in the day, and designed the simplest device to vent the transmission effectively.

    If you look to the page that I posted the illustration from, it says "Note: When the breather bore points in the wrong direction, oil can spill through it".
    The breather isn't baffled, but has an angled extension at the bottom which acts as a shield. When pointed in the wrong direction, it can direct oil up through the breather and out the transmission instead.

    The illustration I posted is from the factory manual, page R 50. Do you have a factory manual to refer to as you take the various things on your transmission apart?

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    Jon B.
    Vista, CA

  8. #8
    Member AKAMick's Avatar
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    "The illustration I posted is from the factory manual, page R 50. Do you have a factory manual to refer to as you take the various things on your transmission apart?"
    The only manual I have is Waynes engine book and a Haynes repair manual, Waynes engine book is excellent but the Haynes is lacking, What are the recommended publications and where are they sourced for early (70 T) 911's?

  9. #9
    Member #226 R Gruppe Life Member #147
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    I’ve only used the factory manuals, vol I-II contain info on 65-71. All info is supplemental, so first part is 65-68, divided by a supplement beige page and 69-71 is in the later pages. I don’t have my manuals in front of me, 69 could go eather way, earlier or later. Maybe someone will help me here. G

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