Depends on how many miles you put on in the last two weeks. If the original ball joint's stud was loose in its mounting hole, that hole was already wobbled out and the spindle needed to be replaced. The mechanic would have noticed that when he started taking it apart because normally that is a sweat-producing task. A loose stud would have come out very easily.
Since you didn't have that problem before, we'll assume the mounting hole wasn't wobbled out. That would imply the new ball joint's stud wasn't tightened properly. A click-type torque wrench must be used to set the nut's tightness to specs.
Another potential problem is caused when the cotter pin hole doesn't line up with the notches in the "castle" nut when that nut is tightened properly. The proper procedures is ALWAYS to continue tightening it just enough more until the next notch lines up and the cotter pin can be inserted. There are some people out there who think that results in over-tightening the nut, which is just as bad as leaving it too loose. Backing the nut off just enough to get the cotter pin in is not the correct procedure, and it says that on the instruction sheet that comes with every new ball joint.
Another thing to consider is that Ford has a lot more suspension part trouble than any other manufacturer, and at the mileage you listed it is very doubtful the original ball joint was removed two weeks ago. I suspect it was an earlier replacement that may have been tightened insufficiently. That could have started the hole wobbling out and it showed up now with the new ball joint.
I should explain about this hole thing. The stud of the ball joint is about three inches long and tapered. It's about an inch in diameter on the fat end, and perhaps a half inch on the end where the nut threads on. That ball joint is one of two that allow the spindle to swivel to turn the steering system. The hole in the spindle has a taper that matches that of the ball joint perfectly. When the nut is tightened, it wedges the stud in that tapered hole very tightly. That's why it takes a lot of sweat and banging to break it free. When that nut is not tightened sufficiently, that stud can work free and rattle / wobble around. The metal parts wear against each other and grind the metal away. At that point no amount of tightening is going to prevent the stud from coming loose again. The problem for the mechanic is it will appear to be tight when he assembles the parts. Had he known there was a problem, he would have addressed it then. No experienced mechanic would try to save you a few dollars by overlooking this major detail.
Two things can happen when that hole is wobbled out. The nut might be able to be tightened sufficiently, but only half of the stud is getting wedged in properly. The large end is not being supported by the sides of the hole, and a good solid jolt from hitting a pot hole can cause that stud to snap and break. The top of the wheel / tire will flop out on top a real lot and you won't be able to steer as you skid to a stop. The more common problem is with so little support on the stud, it works loose, as may have happened to your vehicle, and allows that wheel to shift left and right on top. A tire wants to roll in the direction it's leaning, so a loose ball joint will cause steering wander.
My next concern is your description of the symptoms seems rather extreme for a loose ball joint stud. My first suspicion is an alignment adjustment was not tightened sufficiently. It's not uncommon for that to happen, and due to the geometry of the steering and suspension systems, a shifting upper control arm, (which the upper ball joint is attached to), shifts one way, which also causes that wheel to turn left or right. The vehicle will follow that leaning tire that wants to roll in one direction, and you see the steering wheel turn the other way due to the shifting relationship between the steering parts.
If it's not too late, my best recommendation is to have the vehicle inspected at a different tire and alignment shop to see exactly what is loose. Tell them about the recent service, but do not tell them which shop did the work. Knowing who did it can taint the way they find fault or lack of fault. You want an unbiased opinion before you make any accusations. If they find nothing wrong with the ball joint, realigning the vehicle should be all that's needed. The bolts that secure the alignment adjustments often get the threads full of dirt and rust. That makes the nuts appear to be tight when in reality they aren't clamping tight enough. That has happened to every alignment mechanic more than once, whether they admit it or not. It has nothing to do with sloppy workmanship.
Monday, August 8th, 2016 AT 8:44 PM