Ford 4500 Control Hydraulics Screeching

[TroyFord4500]

Bought a 1966 Ford 4500 Industrial ... no hoe on it, but has the FEL ... after flushing the system twice, my hydraulic fluid is finally not milky! Issue I'm having though is the controls are screeching ... plenty of power in the hydros but the screeching is annoying/concerning ... after warming up it screeches ... any idea what this could be? Releif valve? Sucking air somewhere? maybe the spool valves? what are some ways to test for different issues ... any and all help would be awesome

I should add that there are no issues until the system runs for a few minutes ... the first few minutes of operation all the hydraulic controls/movement are quiet as can be??

I cant find anyone with the replacement part(s) ... anyone know where I can buy a replacement part, a complete rebuild kit, and/or a decently priced replacement unit?

There's no loss of power with the loader, more of a loud annoying sound than anything.