In fall 2010 I replaced the lower balljoints on my 1994 Cougar with new ones from Autozone. In the process of selling it a year later (fall 2011), I put new tires on it all around; this is when I found that the Duralast balljoints were junk.
I'm sure many of you have changed your MN12 LBJs. Otherwise, I might need pictures to go along with what you are about to read. Did you get Duralast replacements like I did? The new balljoint is pressed into the LCA, then the new rubber dust boot that came with it slips over the top, to hold grease in and contaminants out. Then the steering knuckle is put on top of this... (etc.)
Well, here's the thing- That steering knuckle compresses the rubber boot, making a crease in it around the circumference of the balljoint. It took less than a year for mine to crack right along that crease, exposing a nasty mess of grease and God-knows-what-else. This is not improper installation; this is poor design (under a "lifetime" warranty, go figure).
If you compare the Duralast BJ to the stock one, you'll find the original has a smaller permanent dust boot that is not removed or installed separately, and slides right up through the LCA with the rest of the BJ.
I went back to Autozone for new ones and they brought me two different boxes. They were both the right part, yet from different manufacturers. One was a Duralast like I just described, and the other was labelled "Evergard", which had a smaller dust boot that looked like OEM equipment. The clerk had no explanation for Evergard part; it's just what happened to be in stock that day.
I replaced one side with the Evergard balljoint, then hesitated to install the Duralast on the other side. I don't want this going bad in less than a year, especially not when selling the car to a buddy of mine.
I took the fresh Duralast BJ, and the year-old one just like it, back to Autozone. They refunded the purchase price of the old one under warranty, but when I asked for another Evergard, they could not get it anymore. I returned the new Duralast BJ while I was there and left, not wanting to put it on the car.
I visited the other parts stores in town, finding the same poor design with the big rubber boot at Oreilly and at Advance Auto. Eventually I found myself at a CarQuest and to my relief got what I was looking for.
I bought the good balljoint, and installed it right away. I then took this second year-old balljoint back to Autozone for its warranty refund. I have learned my lesson, but I will still shop at Autozone. Well, that is, if they have a sale on name-brand stuff like Meguiar's wax, or SeaFoam...