40 420 hydraulic 3 point sick plumbing

[tod]

i also installed a 40 420 hyd 3point off a wheel tractor.it was not a big project fab wise but the hydraulic plumbing is giving me a problem ,what i did was ran a 3/8 hyd hose to the top of the unit and tee,d it in to the 3/4 inch line that controls the 831 loader bucket. now the 3point has pressure and works but the hyd oil wants to come up ,out of the reservior and give me a hydraulic BATH, i went to farm barn and went through 15 gallons of hydraulic oil trying to figure out what the heck is wrongwith it?is it the plumbing to the loader control valve?the hydraulic 3point unit has a big plug hole in the bottom of it ,i tried to tee that into the return line to the reservoir tank and no results there either.i tried a 3/8 restricted flow boss fitting ,that didnt work either ,i tried brass ball valves to manually control the pressure ,that didnt work either / it has to be something simple that i just dont know about.anyways ,all the running around to tractor store and farm barns has gotten old and expensive.john deere hasnt a clue either.maybe it needs its own pump? maybe i shouldent of got involved in this one ?its been taking a lot of time and cannot figure out ,any reply will be of help.Tod

[Lavoy]

Not 100% sure, but keep in mind that you are taking a rockshaft housing that was designed for 9GPM at 1000 PSI and you are stuffing 15 or more GPM at 1500PSI into it. It is not going to be ported internally to handle that kind of flow. Also, on a tractor, the rockshaft housing is the reservoir, so that pump is pulling a vacuum on the return line, and there is no pressure inside of the large cavity. Now you have a very high flow rate going in, and nothing scavenging the oil back out, so it has to be forced out through what was formerly the suction line under pressure. The rockshaft housing is not a sealed reservoir, so the oil is building up and blowing out the fill plug/breather on the top of the housing I would guess.
Lavoy

[tod]

Not 100% sure, but keep in mind that you are taking a rockshaft housing that was designed for 9GPM at 1000 PSI and you are stuffing 15 or more GPM at 1500PSI into it. It is not going to be ported internally to handle that kind of flow. Also, on a tractor, the rockshaft housing is the reservoir, so that pump is pulling a vacuum on the return line, and there is no pressure inside of the large cavity. Now you have a very high flow rate going in, and nothing scavenging the oil back out, so it has to be forced out through what was formerly the suction line under pressure. The rockshaft housing is not a sealed reservoir, so the oil is building up and blowing out the fill plug/breather on the top of the housing I would guess.
Lavoy

sounds logical ,i think i need to search for a remote pump. i thought i would get more replys though ,,,not many people out there experimenting in hydraulic 3points .or not to many people know what im talking about.

[Lavoy]

If you have a gas crawler, you could install the factory hyd pump with no real problems and use it for the 3PT.
Lavoy