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can the front diff suck the grease in from the knuckles?

Discussion in '80-Series Tech' started by e9999, Mar 14, 2004.

  1. e9999

    e9999 You want to do what...? Moderator

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    there was an interesting post by Doug recently about his take on how the front diff will suck grease in through worn axle seals when it generates a vacuum.
    Interesting concept!
    Is that a well-known fact or Doug breaking new ground?

    turns out I checked the front diff oil yesterday, it was black and greasy looking. Annoying! Yet, there is no indication of leaking at the knuckles. Could this resullt from overfilling the knuckles too?

    So according to Doug's theory, this could be caused by the vent being plugged. Tried to look under there (no FSM yet) and saw that the vent is going to some sort of smallish boxy part. Perhaps some valve affair?

    Soo, how do I make sure this vent is not plugged and how to unplug it if it is?

    thanks
    Eric
     
  2. Riley

    Riley

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    [quote author=e9999 link=board=2;threadid=13122;start=msg121032#msg121032 date=1079296681]
    there was an interesting post by Doug recently about his take on how the front diff will suck grease in through worn axle seals when it generates a vacuum.
    Interesting concept!
    Is that a well-known fact or Doug breaking new ground?

    turns out I checked the front diff oil yesterday, it was black and greasy looking. Annoying! Yet, there is no indication of leaking at the knuckles. Could this resullt from overfilling the knuckles too?

    So according to Doug's theory, this could be caused by the vent being plugged. Tried to look under there (no FSM yet) and saw that the vent is going to some sort of smallish boxy part. Perhaps some valve affair?

    Soo, how do I make sure this vent is not plugged and how to unplug it if it is?
    [/quote]

    >> Is that a well-known fact or Doug breaking new ground? <<

    Eric - I'd say pretty well known. Very resonable because the diff can create vacuum.

    >> Could this resullt from overfilling the knuckles too? <<

    Yep, at least that's what I've heard and makes sense.

    >> Soo, how do I make sure this vent is not plugged and how to unplug it if it is? <<

    Read up on the breather hose extension mod. Basically you want to remove that black box and run a new longer hose up into the engine compartment. Cheap mod and well worth it. Somebody should have listed this mod in the FAQ list of cheap mods but we probably all forgot. It's not very exciting but functional.

    Riley
     
  3. e9999

    e9999 You want to do what...? Moderator

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    thanks,
    what is this black box thing?
    found some info on the diff breather extension mod so will look into it, if that will help prevent grease getting into the oil...
    E
     
  4. RavenTai

    RavenTai

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    not sure what the box does, I assume it is just hollow? is but the vent cap on top is the culprit for diff vacuum, it has a one way check valve, as the diff heats up it allows excess pressure out but when t cools the check valve keeps air from getting back in creating a vacuum, when I opened the fill plugs on my diffs a sucking sound could be heard as the air rushed in

    good reading on breathers, pay particular attention to the picture of the cap/valve about half way down

    https://forum.ih8mud.com/index.php?board=2;action=display;threadid=1639
     
  5. e9999

    e9999 You want to do what...? Moderator

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    yes, it's a great post.
    Beo, this and some other follow-ups would make a great addition to the FAQ!
    E
     
  6. RavenTai

    RavenTai

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    [quote author=e9999 link=board=2;threadid=13122;start=msg121053#msg121053 date=1079299567]
    yes, it's a great post.
    Beo, this and some other follow-ups would make a great addition to the FAQ!
    E


    [/quote]


    Agreed!
     
  7. Beowulf

    Beowulf

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    Eric,
    Since I stole all the diagrams, the pictures, and the most of the verbiage (gave credit though...) you have my permission to re-steal it, update it with more pictures and follow-ups, and have your name forever associated with the 80 series diff-breather mod.

    I'm hoping to be the one to post a FAQ on the transfer case crawler mod. :D
    -B-
     
  8. e9999

    e9999 You want to do what...? Moderator

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    wouldn't feel right. Rightfully yours!

    just took the breather line off the front axle. Since I was curious to see what would happen, I used a transparent hose for now, just to see if there will be any oil coming out.

    Took the end black box off. Seems completely empty (without opening it). Maybe to store oil going up? Took the cap off. Heard a ping and ended up with a spring on the bench. Afraid I lost a piece someplace in my shop never to be seen again. An additional part besides the cap and the spring (it's a '97)? Probably the "rubber flapper"? How big and what color is this thing, may look for it...

    No vacuum noted when opening things up. Boy that oil was ugly black greasy...

    Btw, why did Toyota put a one-way valve in there (besides avoiding water going in that is...)? Seems odd they would not address this vacuum issue...

    E
     
  9. Pitbull

    Pitbull

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    [quote author=e9999 link=board=2;threadid=13122;start=msg121289#msg121289 date=1079324464]

    Btw, why did Toyota put a one-way valve in there (besides avoiding water going in that is...)? Seems odd they would not address this vacuum issue...

    E
    [/quote]

    maintance feature for the guys that never change their diff fluid, with this feature they suck grease into the diff to keep everything going :eek:
     
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