I drained mine to replace seals but only because I had just purchased the tractor and the previous owner had never changed it and the hour meter was passed due.
Mine was leaking from the seal of the differential lock shaft. Follow the red pedal back to see where it goes in. If you can degrease the transaxle you could dry to see where the trail comes from easier, and if you are going to replace the seals it might as well be clean first anyway. I ended up...