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Thread: d6c steering

  1. #1
    Join Date
    Jul 2018
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    Tasmania Aistralia
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    Default d6c steering

    Hi all,Ive got a d6c which is not steering. I posted some pics a couple months ago those that might remember. Ive searched the forum on other d6c steering posts to try and diagnose mine to no avail.

    So it will not steer without really stomping on brakes. Pull both levers pointing uphill, or with blade down and it carries on straight ahead like nothing.

    Now ive changed all 4 bearings between the clutches, set preload and backlash according to manual. Replaced all 8x nylon white plastic rings ,and the o ring that sits between the pilot and shaft. Clutch pack was within wear spec.

    Pressures: Had 275 psi at top of steering unit. Same at elbows. Did up pressure to 315, max according to book, didn't change anything. One thing that might not be right is that pressure fluctuates very rapidly about 20 psi, needle on gauge is never still. When i pull levers with gauge hooked up to top of the box, it quickly dips and then comes back up to max pressure, as i'd logically expect, taking up volume/ slack in the oil tubes. Current oil is a little dirty and has some moisture in it, thanks to a leaking oil cooler. Screen is clean.

    Machine has sat for 10 years, with very dirty oil in transmission, dad reckons steering was a little draggy but nothing serious when he parked it.

    So what i don't understand is that its apparently getting pressure to the clutches, without major leakage, and its just not steering. Its so simple I'm stumped as to why its doing it!!!

    The only things i can think of is that the pistons are somehow worn and binding without extending fully, or the clutch packs are stiff/ locked together from sitting for a while somehow. Appart from that im clueless. While the piston/ pilot seem like a sloppy fit to me, i dont see how they could wear to such an extent, there is no visible wear and I compared them to a second set at a local parts place and saw no difference.

    Anyone got any ideas?????? Id usually start throwing money at this stage but i dont even know what to throw it at !!!! Thanks everyone.

  2. #2
    Join Date
    Nov 2006
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    Faunsdale, AL USA
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    3,967

    Default

    Is it usable? Sounds like it needs polishing up a little.

    Can you pull both steering clutches back at once on it like you can on the old ones. If that doesn't stop it, stand on the brakes or lower the blade and stop it so the clutches have to slip. It should soon polish up the plates nicely.

    I am thinking the steering clutches are still dry on those or are they oil type? If they're wet clutches, the moisture in the oil may be the root of your problems.
    D2-5J's, D6-9U's, D318 and D333 power units, 12E-99E grader, 922B & 944A wheel loaders, D330C generator set, DW20 water tanker and a bunch of Jersey cows to take care of in my spare time

  3. #3
    Join Date
    Nov 2006
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    Corralitos, Ca.
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    What clutch pack thickness spec. are you using?
    Wasn't easy to find: 7 new lined discs and 6 new driving plates = 2.008 - 2.190"
    Minimum thickness = 1.80"

    Pressure to steering clutch control should be 265 - 300 psi @ low idle.
    Pulsing needle means you are probably lifting relief valve.

    Any difference in reverse steering? Could indicate disc teeth are hanging up on worn drum splines.
    Last edited by Old Magnet; 05-15-2019 at 02:57 PM.

  4. #4
    Join Date
    Jul 2018
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    Tasmania Aistralia
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    Default

    its got wet clutches in it, 56j serial.

    My book says 2.012" to 2.222" for eight new disc assemblys and 7 new discs. Min is 1.80" mine are about 1.90".

    No discernible difference forwards / reverse.

    Ran the machine a bit today, and it now seems to be working better when hot. Comes to a gradual stop now on a gentle uphill slope, still not great. Should check pressures when its hot.

    Is the pulsing of relief valve anything to be concerned about? I found some vids of a d6c with pressure gauges hooked up on steering clutches and the needles are still.

  5. #5
    Join Date
    Nov 2006
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    Corralitos, Ca.
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    OK, without you stating what the s/n was I was thinking you were working on a 76A.
    Agree with the clutch pack specs but I think your pushing your luck working with the last 0.010" of wear allowance. Why would you want to do that when your already in there?
    There is no pressure relief valve for the steering controls on the 56J. With clutches engaged oil flow is open to the bevel gear compartment. Control works a pressure reducing valve when disengaging clutches.
    Did you notice your pressure gauge bouncing when you were operating at a lower pressure?

  6. #6
    Join Date
    Jul 2018
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    Tasmania Aistralia
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    Default

    Well according to the manual the clutches are within 50-25% of their life. At the rate the machine gets used that would last a very long time. And i've got it down to a fine art pulling clutches now.

    However I would definitely be changing them if i knew they were causing the problem, but I understand the further worn they are, the less spring tension, and the closer towards the piston they naturally sit? Therefore would be easier to be disengaged? Thats my thought process on it, feel free to correct me.


    And yes pressure gauge bounces at idle too.

  7. #7
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    Nov 2006
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    How about at the lower pressure you had at 275 psi? Did the gauge fluctuate then?

  8. #8
    Join Date
    Oct 2011
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    Corryong Vic Australia
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    What was the cylinder like that the piston runs in, sometimes the nylon rings wear a groove in the cylinder and wont allow the piston to travel, hence not disengage the clutch.

    Wombat

  9. #9
    Join Date
    Dec 2006
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    victoria australia
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    Default D6C Steering System Testing

    Hi Team,
    load scans again for these from my Cat School notes Oct. 1965, copy of photo copied pages in school hand outs.

    Have seen low pressures when release pistons are fitted wrong way around--you should be not be able to see the seal rings and should see the two removal aid threaded bolt holes in the piston thrust face that have to face outwards for the hand pressure pull bolts to fit into for easy removal of said pistons.

    To increase steer clutch pack thickness we used to put an extra steel disc or two in as long as the lined material was not flaking off or worn so much that the oil relief lines were worn off or nearly so.
    If the oil trapped between the discs cannot be expelled the clutches slip some before engaging or are reluctant to release due to suction on the surfaces--oil/air cannot get in to allow release.

    need to be careful to align the cast tubes as doing up one flange fully and then the other will try to bend the tubes and they crack and leak--need to coax them into alignment in increments doing up bolts sequentially on each flange in turn.
    Hope this helps.
    Cheers,
    Eddie B.
    Attached Images Attached Images
    Last edited by edb; 05-16-2019 at 11:21 PM.

  10. #10
    Join Date
    Jul 2018
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    Tasmania Aistralia
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    Default

    Gauge still fluctuated before I turned up the pressure.

    Wearing a groove in the bore. Thats one thing i didn't look at closely. Can't imagine that would not have caught my eye though. Oh well they're probably coming back out anyway... Definitely put them in the right way, threaded holes to outside.

    What are the cast tubes you refer to Eddie? Doesn't sound like anything in my machine! Mine has steel pipes which remove from the top with clutch covers.

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