Hydraulics makes a squeal noise

[Jg1]

I have a Cub Cadet 7195 with a FEL.
I was driving across a field not using my FEL or 3 point hitch and my hydraulics started to make a loud squealing noise. The noise is coming from the valve box under the right fender. When I move the hydraulic control stick into neutral the noise stops. When it's engaged and makes the noise, the FEL and 3 point hitch hardly moves. Has anyone experienced this? Do I need to replace the valve box? Theres no leaks, hoses are all connected, don't see any pinched or kinked lines. I used the FEL before I left and everything worked fine. The tractor was parked in a unheated garage with it being 25 degrees outside. I let the tractor warm up before I left. It's a hydrostatic drive tractor and it moves forward and reverse just fine. Any help would be appreciated.
Thanks,
Joey

 

[Jg1]

It was a pressure relief valve that was stuck. Took it to a Implement shop and they said the O rings were good, they found that the pressure relief valve was stuck. They freed the valve and gave the release valve one turn and gave it back no charge, It took them five minutes. I put it all back together and everything is fine. Now I'm going to change the hydraulic fluid and filters and call it good.