I Put Hydraulic Fluid in my Front Axle

Go ahead, call me an idiot. Maybe I am. A week or so ago I was topping off my hydraulic fluid in my 3540 pst 4WD. While I was "topping off" and already had the hydraulic fluid out, and with my brain on vacation, I filled the front axle with the hydraulic fluid. I can drain it, and refill with the proper gear oil if necessary. However, after researching my mistake online, I realize that some tractors actually use hyd fluid for both. What about the 3540? Do I need to drain and replace, or will it be ok?