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Thread: D7 3T Drive

  1. #1
    Join Date
    Oct 2016
    Location
    Australia
    Posts
    23

    Default D7 3T Drive

    Hello forum, I use a Cat D7 3T for pushing ground in Australia for prospecting. I have started losing drive on my right side track and during pushing the dozer tends to pull to the right. Also the steer and brake at the same time to move right has almost stopped functioning. Is this a sign of a worn steering clutch and is there any adjustment or do I need a clutch pack rebuild?
    Cheers Prospectorgav

  2. #2
    Join Date
    Nov 2017
    Posts
    691

    Default

    i think you are right. rebuild the steering clutches.
    D4 6U,1943 D4 2T,Laplant Choate C41 Carrimor Scraper

  3. #3
    Join Date
    Nov 2007
    Location
    NW Ohio
    Posts
    4,243

    Default

    Check the final drive oil also, does it look gray/silver, milky, dirty? When was the oil last changed?

  4. #4
    Join Date
    Oct 2016
    Location
    Australia
    Posts
    23

    Default

    I have not changed the final drive oil since I had the machine about 5 years. I keep it topped up but the oil looks OK in the filler cap. The gearbox oil had moisture in it as I was getting a white milky sludge build up on the inside of the filler tube and under the filler cap. I have changed the gearbox oil since. Are you saying something might be seizing up in the final drive as it is all gear to gear from the steering clutch through looking at the service book. This is why I am leaning towards something in the clutch system.

  5. #5
    Join Date
    Nov 2007
    Location
    NW Ohio
    Posts
    4,243

    Default

    If the oil looks ok then it should be fine, if it was gears and bearings failing then you would be hearing and feeling some strange noises and the oil would be showing signs. Most likely then the steering clutch disc are worn and the brake band lining may be thin or gone. I assume you have checked the adjustments and booster oil level first? There are some inspection covers on the back case on each side also to look into the clutch case.

  6. #6
    Join Date
    Nov 2006
    Location
    Corralitos, Ca.
    Posts
    15,379

    Default

    Have a go at adjusting the steering clutches and brakes before tearing into it.
    Should have 3" of lever travel when adjusted right.
    On the brakes tighten up the brake band adjusting screw, then run the support screw under the tractor up tight and then back off 1-1/2 turns.

  7. #7
    Join Date
    Dec 2006
    Location
    victoria australia
    Posts
    3,474

    Default First Step, Adjust Steer Clutches

    Hi,
    as OM said, you should first off carry out the steer clutch and brake adjustment before ripping your machine apart--first step of troubleshooting, check and return the machine to factory adjusted specifications, ie, carry out adjustments.
    Also check that the rubber lever bump stops for the operators steer cl. levers are in place and there are no sticks/rocks etc. between them and the operators lever so they cannot fully return.

    Scans, last two, below explain about clearance between steer lever rods and booster piston.

    As the clutch pack wears the adjusted lever clearance diminishes until it is all used up and then the clutch spring apply tension is lessened and the clutch slips.

    Scans below from the Operation and Maintenance Instructions Book, Form No 10481, should help you to adjust the pack linkage in the steer clutch compartment.

    One of these books is vital if you are working this machine--check Ebay as they show up--reprints should be available too but sometimes the pictures are not so good.
    Cheers,
    Eddie B.
    Attached Images Attached Images

  8. #8
    Join Date
    Oct 2016
    Location
    Australia
    Posts
    23

    Default

    Thanks to all. I think i'm thinking the wrong way on how the steering clutch works. I thought when no steering lever or brake pedal was depressed, the clutch pack would be locked or no slippage giving positive drive to each final drive giving straight forward movement. When a steering lever or brake was applied, the clutch for that direction would disengage slightly to slip and give drive to the other side clutch hence giving left or right steer. This is why I am thinking the clutch needs rebuilding as it is slipping with no steering lever or brake pedal applied. I will try the adjustments mentioned.

  9. #9
    Join Date
    Nov 2006
    Location
    Faunsdale, AL USA
    Posts
    4,390

    Default

    You’re thinking correctly......just follow through the logic......

    with sufficient wear to the disks and linings, the clutch pack pressure plate and drum move closer together loosening the spring pressure slightly, but the springs can still compress things tightly enough that it transmits power.

    However, the free travel in the clutch linkage disappears as the pack/stack thickness diminishes. Eventually the free travel is all gone and the control linkage begins to hold pressure on the clutch release bearing all the time and diminish the spring tension applied to the clutch disk stack. This is just the same as “riding” a foot clutch in a car or truck.....bad for the throw-out/release bearing and makes clutch easier to slip.

    So, it begins to slip more easily under load ..... usually first noticed when you pull the OPPOSITE side steering clutch lever and all the power/all the load is applied to just the one side, so the tractor just stops instead of turning away from the weak side steering clutch. Release the clutch on the good/better side and tractor moves off again with mostly normal power. This is because each clutch is normally able to take all the power available from the engine, so when they’re both engaged, even somewhat weak clutches will transmit enough power to drive in a straight line.
    Last edited by ccjersey; 05-19-2020 at 06:43 AM.
    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

  10. #10
    Join Date
    Dec 2019
    Location
    Pouce Coupe, BC Canada
    Posts
    196

    Default Very Good Explanation !

    Quote Originally Posted by ccjersey View Post
    You’re thinking correctly......just follow through the logic......

    with sufficient wear to the disks and linings, the clutch pack pressure plate and drum move closer together loosening the spring pressure slightly, but the springs can still compress things tightly enough that it transmits power.

    However, the free travel in the clutch linkage disappears as the pack/stack thickness diminishes. Eventually the free travel is all gone and the control linkage begins to hold pressure on the clutch release bearing all the time and diminish the spring tension applied to the clutch disk stack. This is just the same as “riding” a foot clutch in a car or truck.....bad for the throw-out/release bearing and makes clutch easier to slip.

    So, it begins to slip more easily under load ..... usually first noticed when you pull the OPPOSITE side steering clutch lever and all the power/all the load is applied to just the one side, so the tractor just stops instead of turning away from the weak side steering clutch. Release the clutch on the good/better side and tractor moves off again with mostly normal power. This is because each clutch is normally able to take all the power available from the engine, so when they’re both engaged, even somewhat weak clutches will transmit enough power to drive in a straight line.
    very good explanation CC, i never thought it thru that far but it makes total sense when you operate, and see the parts operate/ repair etc ...
    Caterpillar D6C 99j

    Tax me, I'm Canadian

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