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205 Vent Tube Questions

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by 1Blazin71, Jul 22, 2001.

  1. 1Blazin71

    1Blazin71 1/2 ton status

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    I went to the dealership and got some o-rings for the speedo cable assy. and am trying to seal up the leaks there. I hit it with some RTV and seems like I got it sealed up good.

    In trying to figure out why the speedo cable leaks, I suspect some pressure is building up inside the 205. I recall some people talking about a vent tube. I searched all around my 205 (albeit without dropping it) and cant find any vent tube. Not even a fitting that seemed as though it might have once had a vent tube on it.

    Is it possible that some 205s did not have vent tubes? I felt around on the top passenger side of the unit and did find a 3/4" plug/bolt. I removed it and find that it is hollow down the shaft about a 1/4" and that the hole it screwes into seems to contain a secondary inner sleve which looks to be plastic (using a mirror).

    It is possible that I have found where a vent tube should go? If so what kind of fitting should go here?

    Help appreciated.


    Matthew Meyer
    matthewm@inhollywood.com
    '71 Ochre K5 - 4" Lift 35"s
    ZZ4 350 - 700R
     
  2. JungleBoy

    JungleBoy 1/2 ton status

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    Matthew

    I think you have pulled out one of two poppet nuts on top of the case. You probably don't need those out unless you're pulling the shift rails. My 71 GMC has a vent on the tailshaft housing ("rear output assembly") of the TC, about 8" above the speedo connection, and just slightly on the passenger's side of the upper portion of the tailshaft...
    The vent appears to be a run-of-the-mill vent assembly like you will find on non-4wd differentials.
    JB
     
  3. k5blazerus

    k5blazerus 1/2 ton status

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    I have one on top of the case above the rear out put shaft.

    IF its not broke , break it and upgrade it.
     
  4. NuBombs72K5

    NuBombs72K5 1/2 ton status

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    I just took my 205 to a shop to be checked out. I didn't have a vent tube on mine. I have the same leak at the speedo gear. The guy who is working on it has a 72 Jimmy and his leaks. He said this is a regular occurance. I'll ask about the vent tube. I'm going to pick it up tomorrow so I'll let you know.
     
  5. NuBombs72K5

    NuBombs72K5 1/2 ton status

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    I picked up my transfer case today and it does have a vent. The vent is on top of the tailshaft just like the others. It is just a vent fitting on top of the housing. There is no tube coming off of it.
     
  6. Steve_Chin

    Steve_Chin 1/2 ton status

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    1Blazin71, the bolts you pulled out of the top of the transfer case are the plugs for the shifter detents. As the others have said, there should be a vent stack on the top of the rear output's tailshaft housing.

    WRT the leak, they all leak out of the speedometer driven gear housing. The housing has no seal in it, so oil leaks right past the output gear's shaft into the cable housing. Later 205s have a driven gear housing that has a recess cut in it that looks to be for a seal. I have one but haven't installed it yet.
     

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