My guess would be the squeal is made by the pressure relief valve in the power steering hydraulic system.
Is everything straight and properly greased in your steering? Maybe a mechanical bind would cause high hydraulic pressure to build up due to the mechanical resistance. I've put a few bends in my steering tie-rod that crosses the tractor behind the front axle by running into stumps and rocks that were a wee bit higher than I thought. :laughing:
There is a power steering filter on my TC40, it's in a large canister just below the power steering fluid reservoir. For my TC40, the power steering fluid used is the same hydraulic fluid as the rest of the tractor, but is a separate system.
Edit:
Sorry, I forgot to say :welcome:
With the engine off, and front wheels off the ground, your front wheels should turn freely from side to side, just like being steered, as I recall. That would be a good way to find out if you have a bind in the steering linkage. If you have a FEL, just raise the front of the tractor off the floor with the bucket, then shut it off. Don't crawl under it of course.