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  1. #1
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    Jan 2009
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    North Windham CT
    Tractor
    BX 2350

    Default Gear lube leaking on mower gear box out of vent

    Hey everybody, Was wondering if anyone would know why oil leaks out of the vent on my 54in fine cut deck gearbox? Ive checked the obvious like the gear oil level and actually took a little out to drop the level but still continues to leak. I do mow some pretty steep hills on my lawn, could that be contributing to the oil leakage? I brought it back to the dealer and they pressure tested the seals and they said everything was fine. Could i take the vent out and put a solid bolt in its place or will that damage the gear box?
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  2. #2
    Elite Member dodge man's Avatar
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    Oct 2008
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    3,939
    Location
    West central Illinois
    Tractor
    Kubota BX2350

    Default Re: Gear lube leaking on mower gear box out of vent

    I have a 60" non fine cut deck and mow some pretty steep hills and don't have any leakage. One thing I have found is that at certain engine speeds, it seems like the belt well go into a kind of harmonic vibration. Leave your belt guards off for a minute and see if you get this vibration in the belt. Just a guess but this could cause the oil to shake out of the gear box.

  3. #3
    Super Member _RaT_'s Avatar
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    Apr 2000
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    Northern CA.
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    Push mower, Snapper 21" 6 shovels, 2 rakes, a pick, 2 pinch bars, a post hole digger (two handle type) and 2 wheel barrows that handle like a Porsche.

    Default Re: Gear lube leaking on mower gear box out of vent

    Heat, expansion, pressure. Everything is subject to this. Do remember that the dip stick typically has a range. If you fill it to the top, you normally see some leakage, nature doing its job. Solution, don't always keep everything topped off to the max. Better to be between or just below the lines then over the line. If it did not vent you would eventually open up a gasket/seal. Your situation is quite normal.

    Quote Originally Posted by RMatty View Post
    Hey everybody, Was wondering if anyone would know why oil leaks out of the vent on my 54in fine cut deck gearbox? Ive checked the obvious like the gear oil level and actually took a little out to drop the level but still continues to leak. I do mow some pretty steep hills on my lawn, could that be contributing to the oil leakage? I brought it back to the dealer and they pressure tested the seals and they said everything was fine. Could i take the vent out and put a solid bolt in its place or will that damage the gear box?


  4. #4
    Bronze Member
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    Jan 2009
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    73
    Location
    New Hampshire
    Tractor
    Kubota B3200

    Default Re: Gear lube leaking on mower gear box out of vent

    I agree with RaT...
    It sounds like you have a new mower, which probably has the oil topped off in the gearbox. I would check the level every now and again. Also, if, by chance, the oil was an incorrect viscosity (thinner) it might be more likely to come out the overflow.
    I would think, however, that what you are experiencing is normal due to heat and expansion. Just keep an eye on it.

  5. #5
    Super Member radioman's Avatar
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    May 2008
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    5,609
    Location
    Ontario, NY
    Tractor
    Kubota BX24

    Default Re: Gear lube leaking on mower gear box out of vent

    This is a good question. My father has MF RFM with same issue and still trying to talk to others about it. He had to replace the gearbox once and rebuilt once. He never had a problem when he first got it till now. The dealer put a breather tube on it to prevent seals from blowing out again, but it still boils over to through the breather tube. I would be watching this thread if anyone has an idea what to check.

  6. #6
    Super Member RickB's Avatar
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    7,590
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    Eastern NY
    Tractor
    Case 885, Ford 4000

    Default Re: Gear lube leaking on mower gear box out of vent

    If the breather is in a bolted cover that can be repositioned, perhaps the cover is installed incorrectly and the breather is in a splash zone from the gears inside. Perhaps the oil is carrying a little water and foaming, causing the breather to vent some oil.

  7. #7
    Super Member _RaT_'s Avatar
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    5,814
    Location
    Northern CA.
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    Push mower, Snapper 21" 6 shovels, 2 rakes, a pick, 2 pinch bars, a post hole digger (two handle type) and 2 wheel barrows that handle like a Porsche.

    Default Re: Gear lube leaking on mower gear box out of vent

    Again, heat, expansion of the fluid and air in the gear box needs venting. In a closed system like your radiator there is a method to allow for this via the cap and the recovery tank. Some gearboxes express themselves with signs of oil at the vent site. No big deal, that's just how it works. The front axle on my kubota does it, the entire transmission on my Kubota does it, its physics. Look at the vent on the rear end of a rear drive vehicle. Unusual to see much in the way of oil there but there is also considerably more real estate to keep the oil from ever getting that far.


  8. #8
    Super Member RickB's Avatar
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    Eastern NY
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    Case 885, Ford 4000

    Default Re: Gear lube leaking on mower gear box out of vent

    Quote Originally Posted by _RaT_ View Post
    Again, heat, expansion of the fluid and air in the gear box needs venting. In a closed system like your radiator there is a method to allow for this via the cap and the recovery tank. Some gearboxes express themselves with signs of oil at the vent site. No big deal, that's just how it works. The front axle on my kubota does it, the entire transmission on my Kubota does it, its physics. Look at the vent on the rear end of a rear drive vehicle. Unusual to see much in the way of oil there but there is also considerably more real estate to keep the oil from ever getting that far.
    And yet most mower gearboxes do not vent oil. Some do; usually with cause, sometimes not.

  9. #9
    Super Star Member Egon's Avatar
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    Nova Scotia, Canada

    Default Re: Gear lube leaking on mower gear box out of vent

    Any chance of water getting in the gearbox? [Condensation]

    Can you extend the vent?
    Egon
    50 years behind the times
    Livin in a
    Worn out skin bag filled with rattlin bones

  10. #10
    Gold Member Happyman's Avatar
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    Kents Store, Virginia
    Tractor
    Kubota Grand L 3940

    Default Re: Gear lube leaking on mower gear box out of vent

    I have a Woods PRD8400 finish mower. I also get some oil through the breather at the top of the gear box. This is normal. Once the fluid level drops a little bit, like others mentioned, it should stop. Only worry if you see oil or debris sticking to the sides and bolts of the gear box. On the top around the breather is just fine.
    I clean the gearbox off once in a while and the oil gets less and less over time. Right now there is no oil coming out and the oil level is just slightly below the fill plug on the side of the gearbox. Still plenty of lubricatin going on in there
    Grand L3940 HST, Wallenstein BX62 chipper, Woods GTR72 tiller, Woods BH90-X backhoe, 724 FEL, forks, 1000lb PTO rotary spreader, Woods PRD8400 finish mower, Leinbach 7' landscape rake, United 7' box blade, Pequea 80 bushel manure spreader, Woods 7' Brush Hog.

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