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Cat 730 ADT - Breather Puking Oil

Discussion in 'Other Earthmoving Equipment' started by zx240lc-3, Oct 10, 2018.

  1. zx240lc-3

    zx240lc-3 Member

    Sep 22, 2016
    Hi Gent,

    Working on a Caterpillar 730 ADT S/N: B1M001977

    Over the summer we have been noticing oil puking from the transfer gear or transmission breather periodically. We had the assumption that roading the truck around was causing some of the issue but in the last month or so the truck has not been driven any long distances and when returned for service the issue is still present. Noticing that our transmission oil is low and the transfer gear tank is over full. We do not appear to have any external leaks other than out of the breather that could be causing the transmission oil to be low.

    Any thoughts on where the two oils would meet that we could have them crossing over? It could be possible that the transmission oil is low because its puking out the breather, what would be a cause for this to happen? it does make me wonder though as I don't think there is that much oil that came out of the breather compared to what is extra in the transfer gear tank.

    Any insight would be appreciated.
  2. Dave Neubert

    Dave Neubert Senior Member

    Jul 19, 2018
    Monroe NC
    Is the transmission and transfer box not connected and use the common oil I thought the oil pick up is in the transfer box and it just drains back from the planetary trans to the drop box. but Iam not real familiar with 730s
  3. Wes J

    Wes J Senior Member

    Jan 24, 2016
    Peoria, IL
    Or maybe the oil is leaking out of one and into the other. Very common on transaxles.
  4. John C.

    John C. Senior Member

    Jun 12, 2007
    Machinery & Equipment Appraiser
    I'm with Dave Neubert in that I don't recall the transfer gears having separate oil from the transmission. I don't have access to SIS anymore but maybe one of the gentlemen with access will be able to look it up to make sure.
  5. Mark250

    Mark250 Senior Member

    Aug 30, 2015
    heavy equipment technician
    As the two breathers are side by side which one is "puking oil"
    Are the correct dip sticks fitted?
    Any thoughts on where the two oils would meet that we could have them crossing over?
    The transfer case oil is separate from the transmission and has its own two section pump mounted on the converter housing.As far as I can remember this is the only place for a possible leak path. but the pump is at the top of the converter housing.
    The pump has two duties, one is to supply pressured oil for the operation of the transfer box and the other section is to scavenge the transfer case oil and send it to the reservoir mounted on the side of the machine
    it is reasonably easy to get to and is worth a look.