Upper Control Arm ball joint threads failure?

There's two things to be aware of. First, these vehicles eat upper ball joints, I suspect because the upper control arm sits at such a high angle relative to the road surface. I was involved with a half dozen owners, including a coworker, who needed to have their upper ball joints replaced every two years. The good news is since you've replaced them already, they're bolted in, not riveted. That makes replacing them rather easy.

The second issue to be aware of is sometimes rather than design and produce a new part, one that is already in production can work with minor modifications. That includes these upper ball joints. On some models the thickness of the spindle is smaller where the tapered stud goes into the mating hole. You'll see part of the smooth tapered part sticking out after the threads have run out too soon. When that is a possibility, the manufacturer of the ball joint supplies two stainless steel washers for spacers. Those go under the castle nut. The additional clue if these are needed is when the castle nut is snug or tightened to specs, the cotter pin hole will be fully visible outside of the notches on the nut.

For the benefit for others researching this topic, here's links to some helpful, related articles:

https://www.2carpros.com/articles/jack-up-and-lift-your-car-safely

https://www.2carpros.com/articles/how-to-release-a-ball-joint

For this job, jack the vehicle under the lower control arm, not under the frame rail. Jack stands still go under the frame, but only as a precaution. If supported there, the spindle will fly outward when the tapered stud is released, then you'll still need to jack under the lower control arm to reassemble the spindle and tapered stud.

Raising the truck's ride height will also lead to early failure of the upper ball joint. You'll see evidence of that in rub marks on the housing and on the stud by the red arrow in this photo. Two-wheel-drive trucks use coil springs, so ride height sags over time, unless the suspension was modified. It's the four-wheel-drive models that use adjustable torsion bars. People have been known to crank them up too high. That puts the upper control arm in a steeper angle, which will lead to binding in that area with the red arrow. When ride height is correct, the lower control arm will be nearly parallel to the ground. I was going to post the ride height specs for you, but GM didn't include a drawing of where to take those measurements, so the values are useless. Instead, this type of ball joint requires an alignment after they're replaced. The specialist should check the ride height before attempting an alignment. If you want to check it yourself, every alignment shop has small books that show every model and year, the height specs, and where to take them.

I added the procedure, again for others who might need it, but also because it shows the torque spec for the castle nut. 61 foot - pounds is specified, but if different, use the spec given on the instruction sheet that comes with the new joint.

If the castle nut is not tightened to spec, or you run out of threads as I described, the tapered stud will not be wedged tightly into the hole. The hammering action will break the stud loose, then it will wobble around and elongate the tapered hole. The pounding will also peel the threads and let the nut back off. Either condition requires replacement of the spindle. If you try to reuse it, the stud will wedge in tightly only right next to the last thread. Closer to the ball and the fatter part of the stud, there will be a gap. By not being supported there, the stud will wobble and come loose again. If you're lucky, the nut will back off and cause a clunking noise. If you're not lucky, the stud will snap. Any time you find a loose tapered stud, both the ball joint and the spindle must be replaced at the same time. If only one part is replaced, the wear on the worn part will transfer to the new one, so nothing will have been gained.

Please let me know if this helps or if you have other questions.

Dandy photo. Thank you. The cotter pin looks too rusty for only 3,000 miles, unless you live in a state like I do where they throw a pound of salt on an ounce of snow. There's pitting too on the tapered part of the stud. Water had to get in to do that. This looks like the castle nut wasn't tight enough or it didn't pull the stud in far enough to wedge it tightly in place. Be sure to inspect the hole in the spindle for the same problem and replace it if you see that, otherwise the new stud will develop the same condition.

The miles you listed are about right for this vehicle. My coworker put on around 45,000 per year with his Blazer and we replaced the upper ball joints every two years for six years. That's way too soon considering these are "follower" ball joints. That means they don't hold up any weight of the vehicle. Their only job is to hold the spindle and wheel upright and in alignment. Your lower ball joints are the "load-carrying" joints, meaning they have the entire weight of the front of the truck trying to pull them apart, yet they'll last twice as long as the less-stressed upper joints. Of my last half dozen vehicles, I only replaced one ball joint. That was on an '88 Grand Caravan lower at 440,000 miles. The only thing that's worse than Blazer upper ball joints are those on Fords. Those vehicles scare me when one comes at me on the highway. I've seen way too many come in on a tow truck with wheels hanging one way or the other. Your Blazer joints do not have a reputation or known history of breaking or separating, just of causing a clunking noise and some minor tire alignment wear. I wouldn't be overly concerned about the first two you mentioned, especially since no special tools or muscles are needed now for the next replacements. I don't have a better answer for the 3,000-mile joint. I don't suspect a metallurgy or manufacturing problem. Once a company like Moog goes through all the work to design and manufacture a part, it costs them extremely little extra to make the part stronger than the originals and to address common issues. I attended a three-day school at their plant in St. Louis and got a tour of their research and development department. You can't imagine the testing their parts go through. Even if you were to buy the cheapest part you can find, no aftermarket manufacturer is going to go through all the expense of design, tooling, and production, then try to save a few pennies if it compromises quality. The only exception I'm too aware of is Ford original steering and suspension parts. As an example, on the '80s Ford-built Tempos and Escorts, outer tie rod ends last exactly 15,000 miles, and the "improved" parts through the Ford dealers' parts departments lasted, exactly 15,000 miles. Only the cheapest aftermarket tie rod ends we could find came with grease fittings and lasted as long as those on other car brands. We called those "killer" cars because so many people went into ditches or oncoming traffic when they lost steering control. One tie rod end even separated as the owner was turning into our parking lot. She never made it past the sidewalk. No other manufacturer has ever had such a huge problem with steering and suspension parts.

I don't know if this makes you feel any better, but there's a lot of car owners who would be happy to get 95,000 miles out of a replacement part.

The only other thing I can think of at this point is I had one in the mid '90s where I replaced the outer tie rod end, performed the alignment, then tightened the jamb nuts on the tie rods. Didn't realize I was tightening the nut against rust that had built up in the threads of the inner tie rod end, not against the outer tie rod end. As a result, the jamb nut wasn't tight enough even though I couldn't turn the parts by hand. Being less than full tightness allowed them to hammer back and forth on the threads with every bump in the road, until after a few months the threads had been worn off both parts and they almost separated. That was when I had been a suspension and alignment specialist for over ten years, and I should have known better, so you can imagine how something similar can happen to a competent do-it-yourselfer. Lucky for me the owner recognized the steering wheel had suddenly shifted off-center and brought it back right away.

Understand too when you find a really inexpensive replacement part, no smaller aftermarket manufacturer can handle the expense of redesigning and manufacturing a part for a safety system for such a relatively limited audience. Instead, they typically buy them in huge quantities from the big guys, like Moog, then put their own name on them. I've seen "inexpensive" engine gasket sets come with the FelPro name on them. One other case I'm aware of is if you buy a replacement fuel pump for a Chrysler product from the dealer's parts department or from Napa, they're the same part. Both Chrysler and Napa buy them from Carter, then they put their own names on the boxes.

The only other exception to my sad story is if there is indeed something wrong with your 3,000-mile joint, that didn't happen to just the one you got. They make thousands of them each day. If the mix of metals and additives was wrong, for example, it would affect a huge batch, there would be recalls, and the news media would be screaming about it. We got to find someone to blame, but I don't think it's the quality of the part. I've had other less-serious problems in the past, and I'm sorry to say they were usually the result of something I did wrong or didn't catch in the initial inspection, but I'll never admit that out loud.

If testing is performed on the old part, please let me know how they do that and what they find. It's always nice to learn something new.

Please clarify that. Ball bearings? Was an old ball joint installed by mistake?