I recently aquired a Case 485. It came with a front-end loader which I had to replace all the hyd. hoses. Naturally, now I need to add fluid to bring my level back up, but I am not absolutely sure where to add the fluid. I see a threaded plug with a square head located at the rear of the tractor, just above the pto shaft. Is this the right place to add, and if not, where is the correct place?