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  1. #1
    Bronze Member
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    Dec 2010
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    John DeereX748

    Default Hydraulic Problem on X748 with Snowblower

    There's a weight box on the back. This problem was there last year, but not as bad. This year with weight in the box, it''s more pronounced.

    If I turn the spout to the left on the snowblower, the 3pt weight box goes down. If I turn the spout right, the weight box goes up. If I turn the spout to the left all the way and feather the lever slowly to turn the spout right, the 3pt goes up first then the spout starts to swing, almost like a master/slave hydraulic condition.

    Ok the obvious answer is "lift the 3pt and close the manual valve on the side of the SCV. Great idea. That's what the valve is for, but the 3pt still drops when the spout is turned left. Closing the valve doesn't help.

    Now, If I lift the 3pt half way up and close the manual valve, the 3pt still goes down when turning the snowblower left. When I turn the snowblower right, the 3pt only goes up half way and stops where it was when I closed the manual valve.

    First guess was the manual valve on the side of the SCV was bad. Nope. valve is good.

    One of the next theories was the hydraulic cylinder for the 3pt or mower deck has a blow internal seal and is just pushing oil back and forth around the piston. I don't think the is the problem, but it is a suggestion.

    Another theory is when I turn the spout left, the 3pt uses gravity and closes the cylinder. This creats something of a vacuum on the back side of the cylinder. When I turn right, oil closes the cylinder. When the cylinder piston reaches the hydraulic oil on the backside, the cylinder stops. So, with the manual valve closed to the cylinder, it's acting like a oneway hydraulic cylinder and power up only.

    That little manual valve on the SCV is on the line it is supposed to be. There would be a lot adapting to make it fit on the other line

    Anyone have a better guess what is going on here.

    While I havent compared the two, a friend has a 435 with a 3pt with a weight bar and blade on the front. He does not have this problem.

    Thanks

  2. #2
    Elite Member zzvyb6's Avatar
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    Dec 2006
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    2,598
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    michigan
    Tractor
    jd 1070

    Default Re: Hydraulic Problem on X748 with Snowblower

    John Deere Parts lookup (you can do this also) shows an optional flow control valve that shuts off lift cylinder pressure to keep the rear lift stationary. Either you have it or you don't. If you do, find it (its right near the valve control block) and close it. If not, you need to add a AM134625 FLOW CONTROL HYD. VALVE between the valve block and the lift cylinder.

    That's all folks !
    There is no "I" in team, but there is a "Me" if you want to jumble it up a bit...

  3. #3
    Silver Member
    Join Date
    Jun 2007
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    119

    Default Re: Hydraulic Problem on X748 with Snowblower

    Have you tried adjusting the depth control rod on the 3PH to not allow movement of the 3PH lift arms?
    2010 JD X728 62C MMM 47" Quick Hitch Front Mount Snowblower 54" Quick Hitch Front Blade 48" KingKutter Tiller
    1990 JD 185 46"MMM with PowerFlo Bagger

  4. #4
    Bronze Member
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    John DeereX748

    Default Re: Hydraulic Problem on X748 with Snowblower

    Quote Originally Posted by zzvyb6 View Post
    John Deere Parts lookup (you can do this also) shows an optional flow control valve that shuts off lift cylinder pressure to keep the rear lift stationary. Either you have it or you don't. If you do, find it (its right near the valve control block) and close it. If not, you need to add a AM134625 FLOW CONTROL HYD. VALVE between the valve block and the lift cylinder.

    That's all folks !
    Yeah, when I talk about a manual valve, that's what I mean. It's #18 to replace #13. It's there instead of the elbow. Expensive little sucker! It is working and not stripped.


  5. #5
    Bronze Member
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    John DeereX748

    Default Re: Hydraulic Problem on X748 with Snowblower

    So when I swing the spout left, it lets oil out of the mower lift cylinder, extends, and lets the 3pt or deck down.


    If I did not have the weight box on the back, I wouldn't have this problem. Unless there is a problem in the hydraulic control valve, it looks to me this is how it is supposed to work.

    Do I need to put another inline flow valve on the other line to shut off oil to both sides of the cylinder? I realize JD doesn't make sell such a valve for this application, the the line can be cut and something installed inline.

    Am I the only one who has this problem?

  6. #6
    Bronze Member
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    John DeereX748

    Default Re: Hydraulic Problem on X748 with Snowblower

    Could there be something wrong in the SCV causing this?


  7. #7
    Bronze Member
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    John DeereX748

    Default Re: Hydraulic Problem on X748 with Snowblower


  8. #8
    New Member
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    Oct 2010
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    John Deere X748

    Default Re: Hydraulic Problem on X748 with Snowblower

    Quote Originally Posted by captplaid View Post
    Could there be something wrong in the SCV causing this?
    There is a similar thread over here http://www.mytractorforum.com/showthread.php?t=166336

    They mention bad valves and have a link to a replacement part.

  9. #9
    Bronze Member
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    John DeereX748

    Default Re: Hydraulic Problem on X748 with Snowblower

    Dang. I'm surprised they had the same discussion today.

    Thanks.

    www.Aux-Hyd.com
    Last edited by captplaid; 01-01-2011 at 11:08 PM.

  10. #10
    Veteran Member CHDinCT's Avatar
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    Connecticut
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    Kubota BX25

    Default

    Just an FYI on that aux-hyd valve. I put that on my old x485 and also had the issue of the 3PH moving with one of the FEL circuits - can't recall which function. Good luck.
    Chris

    2 acres and a mule, er, Kubota BX25, and too many other toys,er, tools to list.

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