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Technical Turbo trans leaking down after sitting awhile?

Discussion in 'The Hokey Ass Message Board' started by rtp, Jul 4, 2022.

  1. rtp
    Joined: Aug 14, 2007
    Posts: 217

    rtp
    Member

    ok not totally HAMB friendly . I built what I had and could afford.
    1948 66 series Oldsmobile . 1972 Oldsmobile 350 ci.350turbo trans.
    After sitting a few days trans is low on fluid seems to be leaking out at dipstick seal. Needs 4 quarts to refill .
    Any transmission guys have an answer?
    Many thanks
    RTP
     
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 52,788

    squirrel
    Member

    search for the many threads on leaking TH350 transmissions....there are about a dozen places it can leak. Shifter shaft, KD cable, diptsick tube, speedometer gear adapter, accumulator cover, etc are a few of them.

    If it's just the diptstick tube, get a new O ring, and install it (no sealer), and see if that fixes it. If not, come back and ask again, we'll see what we can figure out.
     
    Flathead Dave likes this.
  3. krylon32
    Joined: Jan 29, 2006
    Posts: 8,455

    krylon32
    Alliance Vendor
    from Nebraska

    .I just went thru this for the second tine with my 40 coupe. First time it was a combo of the shifter shaft and the dip stick, fixed that and a few months later another puddle. This time it was the speedometer bullet. Is again fixed. Keeping my fingers crossed?
     
    big duece likes this.
  4. miker98038
    Joined: Jan 24, 2011
    Posts: 886

    miker98038
    Member

    4 quarts is a hell of a leak. How long did that take? Any idea?
     

  5. BamaMav
    Joined: Jun 19, 2011
    Posts: 6,027

    BamaMav
    Member
    from Berry, AL

    If it was leaking 4 quarts between driving sessions, you'd have a small lake underneath it. Are you sure it's leaking and not sucking it in the vacuum line and burning it?

    The last Turbo 350 I had leaked at the shift linkage. It would leak maybe a pint in a month of sitting. Bad enoungh that I kept a catch pan under it.
     
  6. sdluck
    Joined: Sep 19, 2006
    Posts: 3,033

    sdluck
    Member

    Was the tran rebuilt?
     
  7. squirrel
    Joined: Sep 23, 2004
    Posts: 52,788

    squirrel
    Member

    If the O ring got cut while installing it (usually due to a badly made repop tube, with the wrong size groove), then it can leak out pretty fast. But there are a lot of other possible sources of the leak, and it's hard to see what's going on when there's that much oil all over the transmission.
     
  8. B.A.KING
    Joined: Apr 6, 2005
    Posts: 4,032

    B.A.KING
    Member

    I had one that would loose 4 quarts. The torque converter would drain and push it out at pump seal. Thats what my trans guy told me. I don't know if thats what it was, but he fixed it.And it would set for a month sometimes. Keep us posted.
     
  9. rtp
    Joined: Aug 14, 2007
    Posts: 217

    rtp
    Member

    Thanks for the replys . Drove it 3 weeks ago trans was full when parked. Started it today not enough fluid to move the car ,added four quarts . Shifts ,drives fine . Can see where dip stick tube enters trans is wet. Rest of trans is dry. 8 months ago pulled it and re did all seals and has been good till now . Seems as converter leaks down . Is that a possibility?
     
  10. big duece
    Joined: Jul 28, 2008
    Posts: 6,608

    big duece
    Member
    from kansas

    Just did that fix on my wifes off topic Firechicken. Shaft seal was weeping, main culprit was speedo bullet and fill tube O ring. Done 25 yrs ago, man time flies...
     
  11. miker98038
    Joined: Jan 24, 2011
    Posts: 886

    miker98038
    Member

    Ok, lost 4 quarts in 3 weeks parked? What was the under the car, dirt, pea gravel?
     
  12. Same problem, installed a new dipstick O ring, and I used a nice layer of sealant (not silicon), let it dry for a couple of days, and seems to have worked. I only put the sealant on there as I had to dismantle half the floor to get to it, and I didn't want to have to go through that (again!).
     
  13. squirrel
    Joined: Sep 23, 2004
    Posts: 52,788

    squirrel
    Member

    O rings don't need sealer to seal. They just need to fit, and not be damaged. Sealer doesn't help them, at all.

    The kickdown cable is near the dipstick tube, and the cable itself can leak, as well as the O ring on the end of the housing.

    I think the cause of the converter draining, is the pump bushing being worn...but that's just a guess. Anyways, the transmission should be sealed well enough that having it drain back, won't cause oil to come out anywhere.
     
    ottoman, VANDENPLAS and Pist-n-Broke like this.
  14. dalesnyder
    Joined: Feb 6, 2008
    Posts: 562

    dalesnyder
    Member

    Don’t forget, the turbo 350 has a vacuum modulator. When the diaphragm breaks it will suck the transmission dry.
    It’s often overlooked
     
    AccurateMike likes this.
  15. rtp
    Joined: Aug 14, 2007
    Posts: 217

    rtp
    Member

    Gravel
     
  16. rtp
    Joined: Aug 14, 2007
    Posts: 217

    rtp
    Member

    Last modulator I had leak like that sent a smoke screen out the tail pipe..
     
  17. rtp
    Joined: Aug 14, 2007
    Posts: 217

    rtp
    Member

    Jim, that's what I was asking about , could it be pump bushing,sealing rings ? Guess I should look in to a rebuild.
    And yeah now I know the dipstick seal is a leaker. Oh well got to get to it I guess.
     
  18. big duece
    Joined: Jul 28, 2008
    Posts: 6,608

    big duece
    Member
    from kansas

    Might be kinda street roddy looking, but positive lock nut on bottom seal into case. But on the other hand, a puddle under the car is not cool at the local burger hang out. 61Imz03CaXL._AC_SL1053_.jpg
     
  19. Bigdavid
    Joined: Feb 10, 2012
    Posts: 39

    Bigdavid
    Member
    from Tennessee

    I just had a leaky new 350 tranny. I cleaned it up really good then threw
    baby powder all around the usual suspects,the one thing I overlooked,
    the kick down cable bolt was loose.
     
    big duece likes this.

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