It drove fine until the alignment
I had new tires mounted at a tire shop on my 1986 full-size Ford Bronco but could not have it aligned at that time. I drove it for two months, and it handled perfectly. Then I had it aligned (toe-in only) and they said I needed one ball joint. I had my mechanic replace all four.
After that, it did not steer correctly. It wanted to wander or dart to one side or the other. I could not drive it without holding onto the steering wheel with both hands. When I turned the steering wheel in either direction and then let go it would continue to turn in that direction, whereas, the steering wheel should return somewhere toward center when released.
I took it back to the tire shop for another alignment. They did only toe-in and it did nothing to correct the problem. The tires, by the way, were at proper inflation. They said I needed a new steering gearbox. Our mechanic installed the gearbox. It did no good.
I took it back to the tire shop and told them it might need to have the caster adjusted. They said, “no, it actually needs a new drag link.” Our mechanic installed a new drag link but that did nothing. I took it back to the tire shop and told them to do a full caster/camber alignment. They did it and it made no difference. They said we need new ball joints; that the mechanic may have put them in wrong. Our mechanic said “no, they weren’t put in wrong.” With linkage removed, the front wheels could barely be moved back and forth. The nut on the alignment bushing was torqued to 100 ft.-lbs. The specs call for 85 to 110 ft.-lbs. The mechanic backed it off to 85 and it was still too tight. He backed it off to 50 ft.-lbs. and that finally made a difference. We drove it and it seemed almost normal. I took it back to the tire shop to see if they may have put in the wrong bushings when they did the last alignment. They looked at it and said, “No, those are the correct bushings, but you shouldn’t leave it torqued at only 50 ft.-lbs.” Do you have any ideas?
You state that it “handled perfectly” after the tires were installed and then after your mechanic installed four ball joints it did not steer correctly. One could easily jump to the conclusion that something is wrong with the ball joints.
You also state that with the steering linkage removed the front wheels could barely be moved back and forth. This certainly indicates that the problem is not in the steering linkage or steering box, but rather is most likely in what anchors the wheel assemblies to the vehicle, namely the ball joints. How those responsible came to the conclusion that you needed a steering box and then a drag link is slightly mysterious to me.
At this point I suggest correctly installing new ball joints to determine if that’s the problem. You can start off doing just one side and see if that helps the one side and if it does, do the other side.
If that does not cure the problem then I would start systematically looking at each thing that could potentially be causing your steering issues to determine where the problem is. Incorrect wheel alignment, or more specifically incorrect caster adjustment, can cause the hard steering
and erratic handling you describe so as a starting point, you should consider getting the alignment checked by another qualified shop just to make sure the alignment is where it’s supposed to be. Then look again at everything else from the steering box to the alignment bushings.