Power steering *popped* then became stiff, squealing on turns

Hi everyone,

I drive a '65 Mustang 289 with the original power steering system.

As I was slowly turning the steering wheel while backing out of a parking spot yesterday, I heard a pop and my steering went stiff. I can still turn, but with a lot of effort and a lot of squealing -- the type of squealing you get when you reach the furthest limit of a left or right turn, except now it happens anytime I turn the wheel. And, as I said, the steering is obviously stiffer, as if the power steering is no longer working.

I checked the engine bay and the belt was still there, and there was no fluid overflow or explosion of any kind. Everything looked normal. I checked the reservoir and there was fluid. And, yes, I'm using the correct fluid: Napa ATF 75-205.

Some background: My power steering (transmission) fluid reservoir has been leaking slowly but surely. I've been topping it off and checking it regularly, but I can confirm that I drove the car at least once a few weeks ago with NO FLUID. After filling it up though, everything seemed fine and I was driving without problems until this happened.

So, in summary, my power steering popped on a slow turn. Now it takes a lot of effort to turn and squeals loudly. What's wrong?