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First thing: HURRAY!!!Sorry right back. That looks like a suction leak to me. What say, arrow?
The charge pump doesn’t provide hydraulic force type pressure. It’s there as a supplement to ensure enough pressure to feed the orifices in the closed loop hydrostatic parts of the tranny. It is a feed element however. As Scotty adroitly mentioned, the thing is rather buried.
So what was happening with that leak was that the necessary pressure of 250-400 lbs to keep the oil flowing where it should have been, was causing a system cavitation which explains your pump whine. A few of us mentioned this aeration at the beginning of the thread. It was just a matter of where it was occurring. When this pressure becomes so low, your pistons where they live against the swash plate are sought of servo protected and Luckily, your pump stayed intact. Basically, your system went into suction.
This was a great thread because it pointed out all the possibilities of why hydrostats might have problems and not be as catastrophic as some may think.
Thank you Len for bringing us this challenge for the benefit of all hydrostatic drivers.
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