Ford 4630 Hydraulics

[detel]

I have a '93 Ford 4630 dsl., 2 wheel dr. that I was bushhoggen with and it felt like I somehow hiit the lever and shut the pto off because the mower started slowing down. I check the lever and it was still in gear so I went to raise the bushhog to take it to the barn but none of the hydraulics work. I check th fluid and it was low so I brought it back to full but still nothing. The pto shaft turns real slow but there is no engaging it with the lever. Any ideas of what or where I might look for the problem? Is there some kind of Knock off switch for the pto to shut down if you hit something? Any help would be appreciated.

Thanks
Michael