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Rear axel under pressure or vacuum

Discussion in '80-Series Tech' started by MH_Stevens, Jul 13, 2005.

  1. MH_Stevens

    MH_Stevens

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    Today when I removed the drain plug on the back diff there was a large rushing of air. Not sure if it was in or out. Does that mean the breather is blocked/
     
  2. e9999

    e9999 You want to do what...? Moderator

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    apparently so
     
  3. Darwood

    Darwood

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    If you look at the flapper valve design on the breathers I don't see how they couldn't produce a vacuum under normal operation. The valve opens when there is presure and then closes when a vacuum occurs. This in turn creates a vacuum in the differential.

    I would say your breathers are "working as designed" for what it's worth. Doesn't mean it's a good thing, just that the part is not malfunctioning.
     
    Last edited: Jul 13, 2005
  4. mabrodis

    mabrodis

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    It must have been a vacuum or you would have had gearlube spray all over you. My friend's 4Runner had a completely blocked breather on the rear diff. I pulled the drainplug and it shot out, I couldn't get the plug out fast enough, it sprayed ~10' in each direction, seriously, it was under a ton of pressure. That was when we found the breather totally rusted/clogged. We were replacing the rear axle seals, since they were leaking, well no wonder with that kind of pressure in there, I couldn't believe they didn't leak more, darn good seals.

    Yes a vacuum condition can occur (driving a long way, gets all hot, then cools, but factory breather won't let any air in), but normally it's not a real big deal I don't think, since if the vacuum got bad enough it'd pull air in from a axle seal or something, which probably wouldn't hurt anything since it's pulling something in, not pushing it out. Ofcourse if you put in new breathers with a gas filter or some other sort of filter on the tube then you'd eliminate any vacuum condition also.
     
  5. MH_Stevens

    MH_Stevens

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    And is that agood thing to do - replace the valve with a filter? Why does Toyota use a one way valve as opposed to a two-way filter? Incidentially there was no pressure on the front axel - I guess there never would be as that must leak air through the knuckle.
     
  6. miked

    miked

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    reminds me of when i first cracked the drain on my front diff. sounded like a bong hit. gurgle gurgle gurgle...droole droole. cept in this case, the droole was 80wt mixed with moly grease.
     
  7. IdahoDoug

    IdahoDoug

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    Yes, remove the evil flappers. Drop a warm axle into a cold stream and if there's a bad seal you'll get water sucked into the axle. It was a good idea from some perspectives, but I feel they should have later modified the elevated axle vent to be an open top for free air exchange. Get .25 inch rubber fuel hose and simply take the existing hose off the axle barb, cannibalize its clamp for your new hose and secure the high end as high as you can. Some run the rear all the way forward and T it to the front diff line. Some anal types even T in the tranny vent as well. Water is death on drivetrain parts.

    DougM