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Thread: D6H scavenge pump failing?

  1. #1
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    D6H scavenge pump failing?

    I think my transmission scavenge pump is going bad. Sometimes when I check the oil level its up or down by about 5 gallons. I got around a gallon of oil out of the torque converter when I took the scavenge line off. After starting it and letting it run for a while I shut it off and removed the cover on the back of the trans, the oil level is around half way up the side of the clutches. Anybody know how much oil is suposed to be in there?

    Some details.

    ser# 4RC108x

    suction screens are clean

    powershift trans, not a diff steer

    runs fine other than the filter bypass indicator comes on at startup when the oil is cold, I have replaced the switch, filter, oil, cleaned out the trans case during some recent repairs, checked pressures and the lines from the torque converter to the oil cooler for debris. when I start it up the indicator comes on within a few seconds and stays on for 10 minutes or so. I'm running an ultra high efficiency filter. anyone else use these filters? When I order the original filter number it has changed over to the ultra filter. Do these restrict the flow of oil more than the old standard filters. I run TO-4 30 wt. The light comes on wether its 30 degrees or 70 degrees out.

    Gotta get this figured out, its driving me crazy

  2. #2
    Senior Member Nige's Avatar
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    Let's start at the filter and the bypass valve/switch end. What Part # filter are you currently using..? What was the original filter Part Number listed in your Parts Manual ..?

    Check the wiring close by your bypass switch. Does it also go to a temperature switch..? See below which is copied straight from a Cat Service Magazine article entitled "Troubleshooting Filter Indicator Switches"

    There is generally nothing wrong with almost every switch replaced in the field. These switches are frequently replaced in error because the bypass spool was not moving freely and (sticking on dirt or debris) causing the switch contacts to OPEN and indicate a plugged filter.

    The root cause can also be the temperature switch. To prevent nuisance restricted filter indications when the oil is cold, a temperature switch (mounted in the filter fluid flow) is connected in parallel with the filter indicator switch. The temperature switch contacts are CLOSED at oil temperatures below the normal operating temperature of approximately 52C (125F) for the transmission oil filter. As long as the temperature switch contacts remain CLOSED, the filter indicator switch can OPEN without causing the filter alert indicator on the monitoring system to FLASH. When the temperature switch contacts OPEN, the filter indicator switch takes over control of the filter alert indicator.


    So check your temperature switch and it's associated wiring. That may be where your problem with your plugged filter warning lies. How many hours on the machine or on the converter if different to machine hours ..?

    Once you've got that cracked we can move on to the torque converter scavenge pump.
    I'd love to see things from your perspective but unfortunately....... I find it impossible to get my head that far up my a$$.

  3. #3
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    Nige,

    Thanks for the reply and the info. I didn't know about the temp switch, it looks like its located in the end of the charge pump. I unplugged the pigtail and put a jumper wire across the harness side contacts and the alarm turns off. I will have to test the temp switch out to see if its working tomorrow.

    My parts book calls for a 9W6428 filter element. The filter in it now is a 132-8876.

    I'm not sure of the actual hours, I've put 2350 hours on it since I bought it used 15 years ago. Its history prior to that is unknown. My guess from the wear on the blade and pusharms would be 7000 hours total. Just a guess. I went through the trans, steering clutches and brakes recently. Some of the friction disks and plates were worn out. I didn't do anything to the torque converter.

  4. #4
    Senior Member Nige's Avatar
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    9W-6428 is just an old part Number of high-efficiency filter. Also you could find listed 9W-2933, 126-1806 or 139-1534. All service to 132-8876 which is the latest Part Number. 132-8876 is rated at 6 microns. If you want to put a 20-micron filter the same physical size you could use a 1R-0778.

    For your sake I hope it's the scavenge pump but I suspect it could be your converter starting to leak internally but we'll have to figure out a leak-off test procedure to prove it.
    I'd love to see things from your perspective but unfortunately....... I find it impossible to get my head that far up my a$$.

  5. #5
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    Thanks for pointing me in the right direction! I put in a new temp switch in today and when I started it up no filter bypass alarm. Woop! I found some damage to the wiring harness and the guard that encloses the pump drive shaft had cracked all the way across on the bottom. I welded up the guard and put the new deutsch connector on the harness to match the one on the new switch. I'm not a fan of the design of that guard or the location of that switch, not the worse thing in the world to work on, but it could use some improvement. Thought I was going to run out of all my best curse words before I was even half way done.

    Thanks again. Your help is much appreciated.

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