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  1. #1
    New Member
    Join Date
    Oct 2010
    Posts
    1
    Tractor
    1984 John Deere 750

    Default Selective Control Valve

    The SCV for my JD 750 loader has two handles - lift and bucket tilt. I think the SCV cylinder for the lift handle is leaking across its ports because the loader unexpectedly lifts all by itself without pulling the handle. JD wants over $650 for a new SCV (part number PC1873 70-30 or AM197083) and they don't sell any rebuild parts. Does anyone have any ideas on how to fix this? I've removed the SCV and it looks unserviceable. The exposed back end of the piston is round - there are no flats to get a wrench on.

  2. #2
    Advertiser kennyd's Avatar
    Join Date
    Jul 2003
    Posts
    11,658
    Location
    Westminster, MD
    Tractor
    John Deere 4110, 455

    Default Re: Selective Control Valve

    Welcome to TBN

    Your setup looks like the picture below correct?

    I think your best bet is to convert to a new joystick valve, get rid of the hard-lines, mount the new valve in a convenient location, then feed it with hoses.

    You can probably do it for about $350, and you will have a modern style valve.

    This would be a nice valve: https://www.surpluscenter.com/item.a...=1&item=9-7401
    Attached Thumbnails Attached Thumbnails -750-gif  
    KennyD
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  3. #3
    New Member
    Join Date
    Jul 2012
    Posts
    1
    Location
    Canaan, ME
    Tractor
    JD 750

    Default Re: Selective Control Valve

    I know this is an old thread but I also have the same problem that just started with my JD750- the bucket lifts on it's own and you have to hold the lever to bring it back down. I wondered if any of you have done the suggested conversion to the joystick valve, or if you found a way to repair the original valve? I like the idea of the conversion- but have one question- Would this also eliminate the pressure relief valve mounted on the loader arm and fed with hoses from the SCV valve?

    Quote Originally Posted by kennyd View Post
    Welcome to TBN

    Your setup looks like the picture below correct?

    I think your best bet is to convert to a new joystick valve, get rid of the hard-lines, mount the new valve in a convenient location, then feed it with hoses.

    You can probably do it for about $350, and you will have a modern style valve.

    This would be a nice valve: https://www.surpluscenter.com/item.a...=1&item=9-7401

  4. #4
    Elite Member Tx Jim's Avatar
    Join Date
    Jan 2007
    Posts
    4,426
    Location
    Coyote Flats,Tx
    Tractor
    JD 4255/Kubota M7040 HDC

    Default Re: Selective Control Valve

    struell
    If current control valve spools are in neutral position but loader function moves on it's own accord the only "repair" is a completely new control valve.

  5. #5
    Super Star Member J_J's Avatar
    Join Date
    Sep 2003
    Posts
    16,725
    Location
    JACKSONVILLE, FL
    Tractor
    Power-Trac 1445, KUBOTA B-9200HST

    Default Re: Selective Control Valve

    You didn't say if your system is open or closed center hyd system.

    If the centering springs are weak or the nut loose on the spool end the spool could be sliding toward the lift side.

    Centering springs can be adjusted or replaced.

    If the spool is centering, there should be no fluid coming out the work port, and if there is fluid, then the spool is worn beyond use.

    If there is an external relief on the loader lift arms, it is there for extra protection. You may want that adjustable relief depending on the pressure rating of the cyl pressure verses the pump pressure..

    If your hyd system is CC, there is probably one relief valve close by the pump.
    J.J.

    When I works, I works hard. When I sits and thinks, I goes to sleep.

    Git er done.

  6. #6
    Elite Member Tx Jim's Avatar
    Join Date
    Jan 2007
    Posts
    4,426
    Location
    Coyote Flats,Tx
    Tractor
    JD 4255/Kubota M7040 HDC

    Default Re: Selective Control Valve

    JD 750 is open center hyd's.

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