Yes it takes a lot of flow to run a splitter at a decent speed. More than the charge pump on a hydrostatic tractor can put out. The cylinder is also so large it would pretty much use all the oil in the tractor just to push the cylinder out. You also only would have typically 600psi of pressure which isn't going to be very effective unless you used a really large cylinder and then you are right back to the low flow, low fluid capacity problem again. If you have a powered wood splitter with a bad engine you could try to run the existing pump off the pto
of the tractor. With 17hp you could set up the drive so the tractor was running at a lowish RPM and burn less fuel while still having the power to get the job done.