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  1. #1
    Veteran Member Mechanos's Avatar
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    JD 955/70A/7 TLB

    Default JD 70A lift speed issue

    I have a JD 70A loader on my 955. The spec sheet in the manual states the following cycle times:

    Loader raising time: 2.8 seconds
    Loader lowering time: 2.4 seconds
    Bucket dumping time: 2.5 seconds
    Bucket rollback time: 2.1 seconds

    (times measured using a 48" bucket... I have a 60" bucket)

    Bucket cycle times are good, loader lowering time is good, but the loader raising time is slow... about 6 seconds. I checked all of my hydrualic lines and none of them have any restrictors in them. That got me to thinking that maybe the issue is in the SCV, so I switched the two loader hoses at the quick connects and operated the SCV backwards (moved lever to the lower position to raise the loader and vice versa). Loader raising time is still slow and loader lowering time is still good. Anyone have any bright ideas as to what is causing the slow loader raising time?

  2. #2
    Super Star Member J_J's Avatar
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    Power-Trac 1445, KUBOTA B-9200HST

    Default Re: JD 70A lift speed issue

    Maybe the piston seals are leaking in one direction, and not the other. Have you checked the pressure when doing your test. You need to check each cyl, as one of the two cyl, in the parallel circuit might be bad.

    Have you checked the relief valve setting?
    J.J.

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

    Git er done.

  3. #3
    Veteran Member Mechanos's Avatar
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    Default Re: JD 70A lift speed issue

    Quote Originally Posted by J_J View Post
    Maybe the piston seals are leaking in one direction, and not the other. Have you checked the pressure when doing your test. You need to check each cyl, as one of the two cyl, in the parallel circuit might be bad.

    Have you checked the relief valve setting?
    Assuming I would need a Tee fitting to plumb a gauge into the circuit while cycling loader... so no, I have not done that yet.

    I have checked the relief setting... 2450psi.

  4. #4
    Super Star Member J_J's Avatar
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    Default Re: JD 70A lift speed issue

    In checking the relief pressure, did you check each circuit, curl, lift, 3pt.? Install a hyd gage at the input to the FEL valve, and you can monitor and trouble shoot your hyd system for pressure. For flow testing, you need an additional gage.
    J.J.

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

    Git er done.

  5. #5
    Veteran Member Mechanos's Avatar
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    Default Re: JD 70A lift speed issue

    Dumb question... but how would I go about testing each cylinder individually? I'm afraid that if I remove one cylinder from the circuit, the unequal lifting geometry would twist or tweak the loader frame.

  6. #6
    Veteran Member Mechanos's Avatar
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    Default Re: JD 70A lift speed issue

    Quote Originally Posted by J_J View Post
    In checking the relief pressure, did you check each circuit, curl, lift, 3pt.? Install a hyd gage at the input to the FEL valve, and you can monitor and trouble shoot your hyd system for pressure. For flow testing, you need an additional gage.
    Might be kind of hard to do that on my tractor. The hydraulic pump feeds the flow divider with a hard line. The flow divider is a block that stacks onto the two SCV's with internal feed passages to supply the SCV's.

  7. #7
    Super Star Member J_J's Avatar
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    Default Re: JD 70A lift speed issue

    Somewhere in the system, you should be able to tee into any point from the pump outlet to the input to the FEL valve. Then as you activate any lever, you will see pressure developed.

    As far as testing one cyl, just remove both curl rod end from the bucket. then remove and cap one of the curl cyl hose, both hoses to the cyl and activate the lever. When the one cyl is maxed out, the relief pressure will show in the gage. Do this for fwd and rev. Do the same thing to all the other cyl. Remember to remove the rod end connection, so as to not push on the bucket or lift arms. .

    There are ways to tee into steel lines.
    Last edited by J_J; 06-28-2011 at 09:29 AM.
    J.J.

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

    Git er done.

  8. #8
    Veteran Member Mechanos's Avatar
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    Default Re: JD 70A lift speed issue

    Quote Originally Posted by J_J View Post
    Somewhere in the system, you should be able to tee into any point from the pump outlet to the input to the FEL valve. Then as you activate any lever, you will see pressure developed.

    As far as testing one cyl, just remove both curl rod end from the bucket. then remove and cap one of the curl cyl hose, both hoses to the cyl and activate the lever. When the one cyl is maxed out, the relief pressure will show in the gage. Do this for fwd and rev. Do the same thing to all the other cyl. Remember to remove the rod end connection, so as to not push on the bucket or lift arms. .

    There are ways to tee into steel lines.
    Thanks JJ. I'm assuming that you mean I should perform this test on the boom cylinders since my problem is with the loader boom lift cycle time.... but I get the picture. Disconnect rod end, isolate one cylinder, extend cylinder to max., take a pressure reading. Retract cylinder to max., take a pressure reading. Repeat on other cylinder. Reading should match.

    Yes, I can Tee into the system before the flow divider. I interpreted your post to mean immediately ahead of the SCV's. I can't do that, but I can Tee into the inlet of the flow divider which is ahead of the SCV's. I will have to get a length of 1/2" hydraulic hose with ORFS connections at both ends with a gauge Tee'd into it somewhere and just bypass the steel line.

  9. #9
    Veteran Member Mechanos's Avatar
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    Default Re: JD 70A lift speed issue

    My hydraulic fittings arrived. I know have what it takes to tap into the hydraulic line between the pump and the flow divider. Then I should be able to take some readings as J.J. suggested.

  10. #10
    Elite Member dfkrug's Avatar
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    05 Kioti CK30HST w/ Prairie Dog backhoe

    Default Re: JD 70A lift speed issue

    Quote Originally Posted by Mechanos View Post
    Bucket cycle times are good, loader lowering time is good, but the loader raising time is slow... about 6 seconds.
    Just saw this thread.

    If your boom lift time is that slow, and the boom stays up fine, then you
    have one or 2 warn out piston seals. If the boom does not sink visibly
    when you are not touching the joystick, it is not your spool valves. Since
    you have checked your implement pump pressure and it is to-spec, you
    can eliminate pump problems, for the most part. And you have already
    looked for crushed hoses/unseated QDs.

    You can rebuild both cylinders at the same time, or look for which seal
    is the problem. If oil is bypassing one seal a lot more than the other,
    you can detect which one is bad with an infrared temp gun.

    I illustrate the process at post #491 here:
    http://www.tractorbynet.com/forums/p...ebuild-13.html

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