If it is coming out around the PTO shaft it is going to be hydraulic oil and it certainly is not supposed to leak out. You said that the previous owner never used the PTO. I'll bet that it is a rusty as all git-out. I would guess that the rust had worked it way back to the seal and now has chewed it up. I had a 6530C and now a 6640C so I don't know the mechanicals on the 2400 and I don't know if you can pull the PTO final shaft out the back end or not, but, you are likely to need to pull it out sand blast the rust off of the shaft and get the seal area ground and polished. New seal, of course. There after keep that shaft greased all the way up to the seal. I use silicone grease on things like that. It isn't the best lubricant, although it's good enough, but, it is impervious to water, oil, diesel, gasoline and just about anything that you are likely to run into. Also, it doesn't soften or melt with heat. It won't absorb enough water to turn to muck or Mayonnaise. In fact, the only real down side to it is that nothing that I know of will really dissolve it, so it can be hard to clean off. I buy it in 5 oz. tubes as Molykote 111, (Dow-Corning) or as Dow-Corning High Vacuum Grease. You can order it from McMaster-Carr, Inc., MSC Industrial Supply, R S Hughes or most any scientific supply house. At any rate, keep that shaft greased so that rust won't grow back to the seal.