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  1. #1
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    4020 John Deere tractor

    Default 4640 tractor

    I have a 4640 john Deere tractor and after running for about an hour all the hydralics shut down, I changed out all filters and cleaned the screen in bottom of trans. The screen was almost stopped up but clean now, still does same thing when hot after it cools down it starts moving again could it be in main pump or trans pump has anybody ran into this problem before?

  2. #2
    Elite Member Zebrafive's Avatar
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    Default Re: 4640 tractor

    I'd lean towards the main pump. Something getting hot and sticking maybe?
    Trans pump is a pretty simple gear pump.
    It may take more than one filter cange, and screen cleaning to clear things up?
    How old is the fluid? Correct level?

  3. #3
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    4020 John Deere tractor

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    The fluid in it now has been changed to new. I was thinking to remove filters again and screen to double check there , I was thinking if problem still accurs that it may be main pump to .

  4. #4
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    I was wondering if it was in trans pump would it start moving again after it cools down or would it just not move when that one goes out, reason I ask because it is affecting steering and all lifts not just trans

  5. #5
    Elite Member Zebrafive's Avatar
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    Default Re: 4640 tractor

    Tran pump is so named because it is in the trans. The trans is the reservior and it pumps to the main pump suction side. Main pump feeds all hydraulics, steering, 3pt (rockshaft), and SCVs

  6. #6
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    Thanks for the info

  7. #7
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    Deere 110tlb, 4520, x749, x758, L130

    Default Re: 4640 tractor

    It would be good to know how hot the hydraulic oil is when you are having this problem. The reservoir capacity is small considering the flow rate capacity. You may have cooling issues or excessive wear on the pump but there are a few things to consider before pulling the pump. I think that it isn't as likely to be a restriction in the lines or filters as you say it works fine when cool.

    The transmission pump (gear type) is pumping IIRC whenever the engine is running and the clutch is engaged. Don't know how it bypasses when the main pump is out of stroke (no hydraulic functions being operated) and full pressure is reached. Will have to check the drawings to see.

    If it is similar to the 4020 the priority valve shifts at pressures below 1900 psi to steering and brakes only, so does the rockshaft work at startup then it fails shortly before the steering fails?

    Do you have a pressure guage to check the system pressures cold and hot?

    I would also add there is a filter above the drain plug on the bottom of the pump that is about the size of a shotgun shell that I had fail on my 4020, for a 4640 this is part # R27173 on the stroke control assembly. This is easy to check and get to from the bottom of the tractor, remove the drain plug assembly which has a small rod with this filter on it. This small filter screen if plugged up will shut down the pump. If you look at the stroke control in Deere parts it is marked as #17.
    Last edited by jenkinsph; 12-17-2010 at 10:40 PM.

  8. #8
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    Default Re: 4640 tractor

    Does the reservoir, up by the fuel tank run dry when you run out of hydraulic? That would be a mark in favor of a weak trans. pump or a high volume leak downstream. Does this unit have a high/low on the trans?

  9. #9
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    Default Re: 4640 tractor

    When you say after it cools it will start moving again are you referring to the drive train?

  10. #10
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    Everything with hydralics starts working again

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