JD 4520, Toolcat 5610, Bobcat S300, Case-IH 125 Pro, Case-IH 245, IH 1086, IH 806
That is a lot of oil. Surprised it is not draining out the bottom. Your going to have to lift the cab and start looking. Hose? Valve? Loose fitting? May need to wash out entire bottom, clean off everything and start looking.
Wash everything down first, and then add some of that florescent dye to the hyd fluid and shine a black light every where and it will show you the source and trail of the leak. Can be purchased at NAPA.
Sounds like a bad drive motor seal to me. It has filled the chain case up with oil and it is coming out of the top cover. Pull the chain case fill plug on the front of the machine. Oil should not pour out, it should only be filled to the bottom of the plug. If it does pour out, I would suspect a bad drive motor or drive motor seal.