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Thread: D7E 48A noisy scavenge pump

  1. #11
    Join Date
    Nov 2016


    Hey Eddie,
    Thanks for the reply, we aren't really sure which pump is making the noise, either the scavenge pump or the TC recirc/precharge pump. Our best guess is that it's the precharge pump but since both are running in the same housing it's pretty hard to tell exactly which one.
    What you said about the scavenge pump needing oil to not overheat makes sense. What didn't really make sense with this system is how the scavenge pump doesn't end up pumping air and getting a lack of oil. How can it keep enough oil in the TC housing if the converter is new with minimal leakage? Or does the pump never keep up with the leakage and it overflows somewhere?

  2. #12
    Join Date
    Nov 2006
    Corralitos, Ca.


    Scavenge pumps are sized to keep up with TC leakage up to a point where they become over whelmed which floods the TC housing with severe drag on the TC. When everything is new they do suck some air but there is enough oil to not damage the pump. Aerated oil is dumped to the transmission sump where the air can separate from the oil and is vented.

  3. #13
    Join Date
    Jan 2007
    devon uk


    I'm guessing the noise is under the seat, if so it will be oil flow for the steering clutches being exhausted while it is not used and will stop when you pull a lever to release a clutch. The torque ORV pressure is what is held in the torque, the pressure after it should be much lower, I suspect that the cooler is partially blocked, did the converter fail in a big way? There could be debris in the cooler. A pressure after the cooler of 25PSI also seems high, but you have low lube valve pressure? I am wonder if there is a hose in the line which is partially collapsed or a restriction in a solid pipe somewhere, the noise may be related to this, but I would be trying to find out why pressure at the cooler inlet is the same as the ORV pressure first.

  4. #14
    Join Date
    Dec 2006
    victoria australia

    Confused Noisy Transmission Pump

    Hi Team,
    I do not have any Parts Books for these units so am looking at a diagram for an equivalent early D8H with the first Single Stage oil T/C's.
    These machines had a separate Trans Pump mounted on the upper rear of the T/C housing. The T/C Scav. Pump is the pump that is mounted down low under the Trans drive shaft.

    These early machines also ran a separate Steering Pump on the front of the engine rear accessory drive--this was later enlarged and used for both the Trans and Steer systems oil supplies.
    A stethoscope, a long screw driver, dowel, stick held to your ear and the suspected noisy pump can be used to determine which pump is noisy.
    On early machines there are witches hat shaped conical mesh suction screens each side in the lower front of the Trans Case. These are the Trans and Steer pumps suction screens. I think they have yellow O Rings and maybe gaskets as well behind their flanges that can loose tension--they squash down after many years.
    From memory these early machines had removable tubes, that the screens slid into, and they have O Rings at the outer ends--cannot recall if they too had a flange, I think not-- and an O Ring at their inner end as well--later tubes were pressed into the Trans Case. Were these changed as they too can be a source of aerated suction oil?

    There is also a big O ring back inside the Main Steer Clutch Case between the P/Shift Trans and the Main steer case that can often be missed--see attachment--for installation the O Ring is placed on a spigot the engages into the bore in the Trans Case as seen in the Attachment.
    This large section O Ring P/ Number can be hard to find in the Parts Book. This O Ring seals the joint in the suction passage that connects the Trans oil pumps suction system to the rear case pickup under the bevel gear. If left out the pumps suck air and are noisy especially with low oil level and/or climbing inclines. The O Ring P/No is shown on the rear case page--from memory for early Parts Books it may not even be shown but is Noted at the bottom or side of the page.

    Rust holes in the suction tubes and hardened rubber hoses on the suction lines were a problem contributing to aerated suction oil, double clamping helps with modern style constant tension clamps.

    As catsilver and yourself suggest the high pressure reading after the trans oil cooler is puzzling as I would have thought that it should be similar pressure to the Trans Lube pressure, not allowing for restrictions in the supply to the Lube R/V--kinda thinking aloud here?

    Hope this helps.
    Eddie B.
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