Wheel flew off after weeks of cyclical sound?

Logic would dictate this is the result of improper installation, but it's impossible to know which time the damage occurred. We've been preaching since the 1970s the importance of using a click-type torque wrench when tightening lug nuts. Air-powered impact wrenches can easily over-tighten the nuts. That can cause the threads to peel, or the tapered friction surfaces can grind down. Peeling threads show up the next time the nuts are removed, but it's that current mechanic who gets the undeserved blame. Sometimes the nuts won't even come off; they'll just spin. If the threads are not peeled, over-tightening can cause the contact areas of the nuts to grind away, as well as the mating surfaces on the wheel. Once that happens, there's much too little surface area to hold the nuts from working loose. They will loosen as you drive.

The sounds you described are the classic sounds of a loose wheel. Stop driving until the nuts are tightened again, however the damage has already been done. The nuts will likely hold the wheel tight long enough to return to the shop, but the wheel and the nuts must be replaced. To continue driving pretty much guarantees the wheel is going to come off.

The same problems occur when the nuts are not tightened sufficiently. Microscopic movement between them and the wheel grinds the metal away and increases the looseness, ... Which leads to more grinding away.

Another problem can occur when a well-meaning mechanic puts grease on the wheel studs. Many cars, including almost all imports, use: "anodized" studs. That's an electroplated coating that makes them look light blue, light yellow, or silver. That coating is a lubricant. Grease will deteriorate that coating and can lead to "galling". That's similar to the threads tearing away. For regular studs, a very light film of grease is fine, but problems are caused when too much is smeared on. When I do that, I run the nuts on all the way by hand, then use air tools and a torque wrench. When air tools are used to spin the nuts on, the grease can build up ahead of them and gets sprayed outward onto the friction surfaces. Those contact surfaces must remain dry to hold the nuts from coming loose.

Also be aware some do-it-yourselfers will use anti-seize compound on the studs. This is one application where it must never be used. A mechanic caught using it here will likely get fired. The material is so slippery, it almost guarantees the nuts will work loose.

The wheel studs can be replaced without replacing the entire wheel bearing assembly, but it is absolutely required the nuts and wheel must be replaced too. The nuts have a curved friction surface that exactly matches that on the wheel. Those contact points are what holds the nuts from coming loose. If you try to save a few bucks by reusing the wheel, it is 100 percent guaranteed it is going to come loose again. This is one place where even I would not try to cheap out. Be aware when the new studs are pulled in, they may not become fully seated right away. Standard practice is to retorque them within about 50 miles, then perhaps once more after another 50 miles. If they no longer rotate slightly before the torque wrench clicks, they can be considered fully seated and properly tightened. A lot of shops even want to recheck the nuts after they reinstall the wheels after some other service, and they'll ask you to come back in the near future.

For some reason torque specs for your wheels are not listed on my normal source, but from memory, all Front-wheel-drive Chrysler vehicles called for 95 foot-pounds for steel wheels, and 85 or 90 foot-pounds for cast wheels.

The lug studs shear off because once they are loose and the rim can move even a small amount, it starts flexing the studs, Now because they are all not loose or loose to the same degree the tightest one will flex the most as the tire and wheel are exerting a lot of force onto that single stud. Think about the weight of the van as you turn a corner and accelerate. That force flexes the wheel stud and even that small amount will cause fractures and then the stud fails. The forces then go to the next tightest lug. After a while you get to the point where the remaining lugs simply cannot hold the stress any longer and they shear off.
My first question to anyone who loses a wheel like this is, "Did it sound like there was a helicopter nearby". As Doc stated, that wheel is going to need replacement.
As for the bearing seizing and shearing the studs, not likely. I have seen quite a few bearing failures, and they have to get very bad before they will seize up. Then most of the ones I see that did fail did a lot more damage than in your picture. Think about how that bearing is installed. First you have the steering knuckle. To that bolts the hub and bearing assembly which is a cast housing with the wheel bearing inside it. Now the hub gets pressed into the bearings and a retaining collar is welded in place to make them essentially a single part. Now through the center of the hub goes the drive axle. On the inside is the CV joint which is much larger than the bearing, so it cannot pull through the hole in the knuckle. On the outside is the axle nut. Torqued to around 100 ft lb. Or more. So those parts are sandwiched together. Yes the bearing can fail, but in 99.9% of cases it will warn you first, normally with a nice loud growl that gets faster as you speed up. Now I have personally driven vehicles with bad bearings over a year (Read the tale of the cobbler who's children go barefoot to understand that) and when I replace them they are frequently just as tight as the day they were made.
In my opinion this was a case of lug nut's getting loose and shearing off.
Now the reason for wanting to replace the hub instead of just the studs is likely because as they got loose they started rocking in the bores in the hub and made them so that replacements will not pull in solid. The new hub also gets you new studs. As for the lug nuts, I cannot stand the OE nuts on half of the vehicles out there because they use a standard nut with a stainless cap. They look good but corrosion makes the caps swell up and now the OE sized wrench doesn't fit. I suggest replacing them with a better solid steel set. I've used McGard replacements for many years. They have a longer thread engagement and they don't have the cap to swell up. As Doc mentioned there are proper torque specs for them, and for an odd reason I always see the loose lug nuts on Chrysler products with alloy wheels, predominately Jeeps but the vans are a close second. Here the issue is commonly rust. It builds up on the rotor face and corrosion inside the rims seat as well. Put the wheel on, torque it down and it looks fine, but in reality it is setting on that corrosion in a different spot and it works loose. My SOP here is to use a small sandblaster and clean the rotor and hub faces, spray on some fluid film and then wire wheel the rim. Then it goes back together.
Most shops don't do that though because time=money.

If that is as clear as mud just ask for clarification.

Hi brother Steve. Thanks for adding more dandy info. This reminds me of a common problem we'd run into when I worked at a Sears Auto Center in the 1980s. I don't know why, but this only affected GM front-wheel-drive cars, but today I take precautions on all of them. After installing new tires, customers would come back with a complaint of a crunching noise when going around corners during city-driving speeds. The fix was to put a very light film of axle grease on the hub and center hole of the wheel.

To my knowledge, the crunching never caused any other problem, and I suspect it would go away after a while. Cleaning the wheel and the hub with a wire brush did not help. That period, (mid 80s), is also when I saw a coworker use the click-type torque wrench on lug nuts for the first time. Once he told us why, we all bought our own and used them on every car.

The point of my sad story is while that noise didn't lead to some other problem, it can only be caused by two parts moving or rubbing against each other, and in this case, it was the wheel on the hub, even though the nuts were tightened to specs.

One thing we didn't mention is the center hole of the wheel fits exactly onto the hub of the wheel bearing assembly. That is where the vehicle's weight is supported. The studs and nuts only hold the wheel to the face of the hub with the brake rotor sandwiched in between. Once the nuts work loose, the wheel has some play that lets it lift up off the hub a little, so now it's the studs that are holding up the vehicle's weight. With every revolution, the wheel moves up and down a little and saws into the studs. The grinding action will also enlarge the wheel's center hole, so even more movement can occur. This one gave a lot of warning something was wrong. If it can be retrieved, I'd love to examine it and see how much damage occurred.

We still don't know when this started. The second mechanic could have simply reinstalled properly the wheel that was not tightened correctly by the first mechanic. This is where I mentioned over-tightening the nuts can lead to peeled threads, but that won't become evident until years later when the tires are replaced or rotated, then the current mechanic gets blamed unfairly for damage he didn't cause.

BASSMANPETE79, please keep us updated and let us know how this gets resolved.