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Thread: Cat 955L won't push under heavy load

  1. #1
    Join Date
    Sep 2008
    Location
    DuQuoin IL
    Posts
    35

    Default Cat 955L won't push under heavy load

    Hi, I just got another dozer the other day, and it stalls the tracks out under a load, much less than it should. It is a 13x series. Any ideas where to start? I have only checked the trans filter so far, replaced it, no difference. Thanks

  2. #2
    Join Date
    Mar 2007
    Location
    Richmond Hill Ontario
    Posts
    702

    Default

    Hold the center Brake peddal down and shift it through all the gears at full throttle. Then come back with what you find. Pay attention to the engine speed when you do this. A tach would be nice but any idea of the speed will do.
    Later Bob

  3. #3
    Join Date
    Aug 2007
    Location
    Newman Lake, WA
    Posts
    98

    Default

    Similarly, I think I'm not getting as much power out of my D6-9U as I should, so I read this thread with interest. What's the best way to add a tach? With the pony motor I just used a contact tach on the drive pulley. I'm not sure where I would put one on the diesel -- especially since it seems diagnosing really requires it to be under load. Any advice?
    --
    Michael Garrison Stuber
    D6U, #12 Grader, 2 Alpacas, 4 goats, 3 barn cats, a black Russian Terrier, and lots of trees.

  4. #4
    Join Date
    Nov 2006
    Location
    Madrid, Iowa
    Posts
    31

    Default

    For testing purposes, a tach adapter would go where your hour meter is. You could then use a mechanical or electric tach.

  5. #5
    Join Date
    Nov 2006
    Location
    Faunsdale, AL USA
    Posts
    4,418

    Default

    Your direct drive 9U problem could be

    fuel problem, low pressure on gauge, no black smoke as engine lugs down

    air problem, always black smoke at anything above an idle,

    weak engine-lots of black smoke out the exhaust under load, hard starting usually, lots of blow-by out the crankcase breather, various burned valve noises and missing cylinders depending on the cause.

    bad governor- none of the above, certainly not the black smoke, very easy to kill it if you aren't careful, you find yourself nearly always running it wide open.

    Slipping main clutch- tractor slows down under load, especially in higher gears or reverse (which is higer than the corresponding forward gear), easy or no snap on the main clutch lever, engine doesn't lug down as the tractor slows down.

    Slipping steering clutches- usually one before the other, tractor will stop while under load when one clutch is pulled and if severe, may stop with neither clutch pulled, On the oil clutch tractors, you can watch the universal joints behind the clutch as the tractor slows or stops to see where the slipping is occurring.
    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

  6. #6
    Join Date
    Nov 2006
    Location
    Dallas Pa.
    Posts
    1,902

    Default D6 Power

    Many times I,ve found on the old D6s with the D318 engine and lots of other Cat engines is gov. parts worn and esp. the Gov. spring gets weak and won,t advance the rack far enough to get full fuel travel.I have found on the D6 that the 5F6413 spring worked best but the rack travel is .215 where with the 5F1941 is .125 but even the new 5F1941 will help the HP as the book calls for either one of them but have different fuel inj. nozzles. The 5F6413 calls for a 9F4113 nozzle and the 1941 spring calls for a 4F4236 nozzle.

  7. #7
    Join Date
    Sep 2008
    Location
    DuQuoin IL
    Posts
    35

    Default

    Sorry for delayed response, couldn't start machine due to non-related problem. Anyway, I started machine, and as it warmed up condition of tracks stalling out under a load worsens. I put brake on (middle pedal), wide open throttle, and ran through the gears, and basically no change in anything. Tracks still stalled, motor sounds no change.Same thing in reverse 3 speeds.Anyone know what type of oil is used in this machine for the transmission? Any ideas on problem? I'm thinking torque converter, or relief valve, or wrong oil.Thanks for your responses!

  8. #8
    Join Date
    Mar 2007
    Location
    Richmond Hill Ontario
    Posts
    702

    Default

    Check the magnetic screen, in a smaller housing by trans filter. Square cover with 4 studs and nuts. If it's full of metal you need a trans, if it's clean then get some gauges and pressure test the trans. There are 3 1/8"NPT plugs under a round cover on trans top. P1 Speed Clutch should be 350 to 400 PSI, P2 Directional Clutch should 55 PSI lower than P1. P3 Torque Converter Inlet should be 100 PSI at torque stall with cold oil. Check P1&2 with warm oil in every gear at full throttle and at low throttle. The pressure should hold 90% of full throttle value at low throttle. If the pressure control valve is working right the pressures should drop off fast when you shift and built back up to full pressure evenly in 1 to 2 seconds modulation time. Come on back with what you find.
    Later Bob

  9. #9
    Join Date
    Sep 2008
    Location
    DuQuoin IL
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    Thanks, Bob I appreciate your response!

  10. #10
    Join Date
    Sep 2008
    Location
    DuQuoin IL
    Posts
    35

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    I pulled the magnetic screen out, and there is some metal on the magnets, no chucks, just fine stuff. It didn't look like it had been checked for awhile.No signs of recent tampering. How much if any is acceptable?

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