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Faunsdale, AL | Returning to sump severely reduces the system capacity and even if it’ll still run everything the oil will be getting hotter and hotter.
The system is designed with a transmission/charge pump picking up oil from transmission sump screen, pumping it through trans filter and anything not needed for trans lube and clutch operation goes forward to high pressure pump.
This transmission pump typically has about half the GPM capacity of the front pump. It’s there to make up losses from various valves in the system that leak a little to sump and to supply excess to go on through the front pump inlet to the oil cooler. The assumption is that any large flow of high pressure oil to some remote function will return through the SCV and ADD to the oil being pumped through the filter and forward by the transmission pump
So if you return to sump, you start out limited to about half the normal flow rate. Best case it chatters and you don’t keep trying it that way, but if it works you will usually have little EXCESS oil going forward, that the front pump doesn’t pick up, to flow through cooler and back to transmission. The transmission, rear end, lines and pumps become the oil cooler. Really everything BUT the air to oil cooler up front will be hot.
If you have some piddling small hydraulic motor or an intermittent demand like operating cylinders for booms etc, you may get away returning oil to sump, but not with a constant high gpm demand like a big sprayer or vacuum planter etc.
I’ve seen the flow control lever on the SCV be installed wrong and mess up the flow rate you’re trying to set. Have also seen the pin be broken and the lever be spinning on the shaft
Also possible to have leaking SCV’s that bleed off high pressure oil. To check for that, start up cold with nothing using oil and check how fast the SCV housings warm up. One getting hot while the other is cool would be a sign of an internal high pressure leak.
Edited by ccjersey 2/25/2021 13:25
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4630 and hydraulic sprayer pump
