PTO pumps and using the transmission as the reservoir???

[JSharp]

Well the old IH tractors used the transmission as a resivoir for the hydraulics so I don't see why not. Only drawback is you have to keep the pto pump on and lose use of your pto, unless you are putting quick connects on. I would size the PTO pump to the capacity of the storage of the transmission so you didn't encounter the heat issues described above.

If this was an issue they make radiators for hydraulic fluid. (heat exchangers). You could plumb one in to further dissapate the heat.

You also need to make sure that the fluid used by the hydraulics matches the fluid recommended for the tranny.

By the time you factor all that other stuff in you might just want to buy a reservoir and mount it on whatever you are using the PTO pump for.

My IH 404 is built that way. They do add a hydraulic radiator when they're fitted with the larger pump for power steering though. Some of the old IH models even had a front mounted auxiliary pump driven from the engine crankshaft.

I don't think this idea is horrible as long as the OP checks the fluid temp before and after the install and keeps it close. I'd worry more about the pickup exposed under the tractor than anything...