Nearly a catastrophic failure. What could cause lug nuts to self-loosen after front axle rebuilt?

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Apr 24, 2010
North Bend, WA
I tried to keep this as brief as possible but wanted to make sure I include all of the details for clarity sake. I do not want what happened to me to repeat itself to either me or anyone else.

About three weeks ago I rebuilt the front axle and replaced the front brake pads, rotors, and calipers (one was seized). I followed the FSM procedure supplemented with info from the FAQ. During the axle rebuild I replaced the wheel and trunnion bearings. I also disassembled the birfs from the axles, completely cleaned them and swapped sides. I took special care while installing the the steering arm onto the knuckle to ensure there was no binding and also when installing the axle hub to make sure it was fully seated prior to setting the bearing pre-load using the fish-scale method. In short, everything seemed to button up as expected during reassembly. The front wheels were re-installed and torqued to factory spec for alloy rims (76 ft. lbs.)

After the rebuild I drove the truck for approximately 100 miles to make sure everything was working as it should and then embarked on a 1900 mile road trip that took me and my family in a loop from western Washington through eastern Oregon, central Idaho, southwestern Montana, northern Idaho and back into western Washington. It was mostly highway driving with some forest service roads to get us to some of the camping spots (i.e. no rough 4x4 terrain).

For the majority of the trip the truck handled as expected. Every so often I would hear a scraping noise coming from what sounded like the right front when making a left hand turn. I chalked it up to being a the dust shield scraping against the newly installed rotor.

During the last leg of the trip (Post Falls, ID to North Bend, WA) I notice a wobbling sensation (felt like a flat tire) when getting back onto the freeway. It stopped once we got onto the freeway but I felt it again while exiting the freeway in Ellensburg to refuel. Those of you familiar with this drive will know that, with a few exceptions, the drive from Post Falls to Ellensburg is mostly flat and straight.

When exiting the vehicle I noticed one of my front driver side lug nuts lying on the ground. Upon further inspection, and to my absolute horror, I discovered that in addition to the lug nut that was lying on the ground I had a wheel stud that was completely snapped of, was missing another lug nut, and two of the three lug nuts that were remaining on the wheel were loosened to the point were I was able to remove them from the wheel using only my hand. The wheel was so loose that the five remaining wheel studs had begun to grind away at the lug holes in the aluminum rims. I suspect that this force is what caused one of the studs to snap. Essentially, I was extremely fortunate that I didn't loose the wheel completely while driving down the freeway at 70 MPH. I re-torqued the remaining four lug nuts back on to the wheel and cautiously drove the remaining 70 miles home. Probably not the wisest thing to do but I reasoned that I had driven approximately 2000 miles since the rebuild and approximately 300 miles since first noticing the wobbling sensation (I suspect that most of the lug nuts on that wheel were already loosened by that point) so if I re-torqued the remaining ones I could limp my way home without incident, which was the case.

So that's the long-winded back story and now to my question. Other than not getting the wheel properly installed and torqued properly onto the hub after the axle rebuilt (which I don't think is the case) is there something else inherent to a front axle rebuild that I would cause the lug nuts to loosen by themselves? My only thought is that despite me talking extra care I didn't fully seat the axle hub when reinstalling it and so the bearing pre-load was not set properly and perhaps the wheel bearings are loose. But I would think that something like that would cause issues long before the approximately 1700 miles I drove prior to me noticing the wobbling. I haven't torn into and inspected it yet but I want to know what I should be looking for to make sure this doesn't happen again.

So, the first question one must ask is; are the wheels factory alloy? And did the vehicle come this way to you? Aluminum wheels, factory and aftermarket often times require different lug nuts, have a couple boxes of lugs from the PO of my vehicle who had gone from Alloy to steel. Meaning, if someone went from an alloy to a steel and changed lugs as they should have, then someone put alloys back on, that would in itself cause the aforementioned issue. Otherwise, if it's an aftermarket alloy, you should ensure your lug nuts are the recommended design and also check into the recommended torque spec, because often times aftermarket wheels will have their own specific torque rating. Glad everyone is ok, make sure you replace your studs with quality ones. I would suggest Toyota, simply because past experiences with aftermarket fitment. Other than this I would propose that maybe you clean all studs, lightly lubricate them and use a certified torque wrench next time, remember... Torque wrenches don't just stay set, they have to be inspected and re-calibrated after a while. And never use a Harbor Freight or cheap one, also bad experiences. Had a new one checked out at Lewis McCord (I am a former marine) when I had to go with the motor T mechanic on the reserve staff in Oregon to get his stuff certified. They checked it and laughed at how off it was.
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Probably two separate issues. If it was a loose wheel bearing -- you'll know when you take it apart -- you would likely have had some death wobble at some point. But for the most part, it runs fine. Death wobble can often be initiated by a good strong stop, you'll think warped rotor, but it's not. Anyway, you can verify.

As scottyryana noted, recheck those lugs after 100 miles. Things seem to have spun well even when they would seem not to be any longer capable. The hub was turning well, but what was attached, not so good. I'd almost bet the care you took with as evident in your notes turns up OK hub status.

On alternative lugnut torque settings, keep in mind that the studs are obviously rated to the 108 ft lb (IIRC, since I just recently looked that up for mine -- it's heck getting old, beats the alternative, though) for steel lug nuts, so you would want to treat that as a practical upper limit whatever you attach I would think.
Are the lug nuts correct? I mean do they have correct shape to match that of the rim? A long time back during testing at the Abbeerden proving grounds we kept get loose lugs nuts. Finally someone figured out that the lug nuts had the incorrect profile and that they could never be properly seated no matter how many times the torque was checked.

A Few Facts About Lug Nuts - Performance Plus Wheel and Tire
Thanks for the input. No, I did not check and re-torque after 100 miles, my bad. I should note that all four wheels were removed (replaced rear rotors and pads as well). The driver side wheel is the only one where the the lug nuts self-loosened.

They are factory alloy rims with the correct lug nuts (washer type). They were torqued on using a Kobalt torque wrench that I bought at Lowes a few years ago. Which admittedly, I've been meaning to get re-calibrated. I plan on replacing all six studs and lug nuts with Toyota OEM. I reckon I'll also need to swap out the rim with my spare and source a replacement since the lug holes of the one that was on there are no longer round but now oval shaped due to the studs grinding into the rim.

When I begin the inspection my first step will be to mount the spare and check for wheel bearing play using Landtank's 12 and 6 o'clock tug method (should have done this when reassembling the first time around). I'll have to disassemble the hub to install the new studs so I'll also inspect the wheel bearings for any damage. I'm still curious if play in the wheel bearings due to the hub not being entirely seated would cause the lug nuts to self-loosen.
As far as I can tell there is no where in the FSM that specifies using a wet or dry lubricant on any fasteners much less the wheel studs. Also consider that the torque ratings given are always DRY. So when you use a lubricant (anti-sieze, moly, light oil) you have effectively changed the clamping force on the given torque spec needed for the dry torque.
I didn't use any lubricant on the wheel studs. Never have and don't plan on it when reinstalling.
Studs not fully seated, if your not sure always torque the rims like 5 times to make sure stud is pulled fully through, I also torque rims to 85
Studs not fully seated, if your not sure always torque the rims like 5 times to make sure stud is pulled fully through, I also torque rims to 85

I have no reason to believe that the studs weren't fully seated. They were fully seated when the hub was disassembled to install the new rotor and wheel bearings and I didn't replace the old studs with new ones (although I will be now). Are there any forces that I would have exerted on the studs during reassembly that would have caused them to become unseated? I can't think of any.
I don't think that is correct. The studs are seated in the ring which the rotor is bolted to. It is not necessary to remove Nd reseat studs when swapping rotors.

You are correct. I did not need to pull the studs to replace the rotor. The rotor is attached to the axle hub with six additional bolts.
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As far as I can tell there is no where in the FSM that specifies using a wet or dry lubricant on any fasteners much less the wheel studs. Also consider that the torque ratings given are always DRY. So when you use a lubricant (anti-sieze, moly, light oil) you have effectively changed the clamping force on the given torque spec needed for the dry torque.

While true, and assuming clamping force = lug nut wheel interface force, it will only increase the clamping force. The reduction in friction between threads will allow more torque to get to the lug nut wheel interface, opposed to being a force which needs to be overcome. At the end of day, if the stud is clean of corrosion, the a reduction in friction most likely has a very small effect on the clamping force, albeit, it would be greater, ceterus parabis. I think this was what you were getting at....?
Yes. Keep in mind, depending on the lubricant used it will greatly affect the clamping force required. Simple clean oil could reduce the required force by half. Going to full dry spec torque, when lubricated...could be enough to over stretch a wheel stud. Side issue of course.

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