Zero turn hydraulic pump

[j warren]

Thanks for being here to ask questions!
I have a cub cadet commercial tank zero turn (model 53BB5DAV750) with 306 hours on it. It was working fine and i decided to serviced it with new belts, blades, etc. and change the hydraulic oil. After completeing the service the mower ran fine for approx 1 hr and then the left wheel stopped pulling. I am puzzled why the wheel stopped pulling since the mower has been maintained well, this being the second time changing the hydraulic oil and the manufacturer recommends changing in 500 hrs. Could i have trapped some air in the line? I was careful in trying to fill the filter with oil before installing during the service. What do you recommend or suggest?
Thank you!
J Warren

[chance123]

I'm not familiar with your machine, but if it operated fine for an hour, surely all the air has been purged from the system. Do you have one or two hydro pumps?