Power steering pump question

Hey guys, I've got a question. So I've been working on this 88 dodge d100 I recently bought one thing I've noticed but haven't gotten a chance to mess with until now is when I turn the steering wheel all the way left or right (like max lock side to side) the belt was squeaking. So I checked it and noticed when the wheel is turned all the way the power steering pump locks up. Like the pulley completely stops turning. That's why the belt is squeaking. I was thinking it was an alignment issue allowing the wheels to go too far In one direction but it's both ways left or right. What could cause this? Worn tie rod ends, centerlink joints etc ? Or is it a faulty pump? I checked the fluid and topped it off and it didn't help. I'm getting ready to replace all the steering and suspension components in the near future so I guess we'll see then if that helps. I'm thinking it's something in the pump loosing pressure or something to that nature. Let me know if you've ever experienced this. Thanks