Mechanic ReUsed Axle Nuts... Bearing Wrecked

[Seagull]

I had sent my car in to a very reputable, well trusted shop to get the subframe reinforcement done. I usually do the work on my own cars (for reasons reinforced here within) but I dont have access to a welder so I bit the bullet. About a week goes by and they ran into this or that, had to order a part or two because they noticed it needed replacing, etc. Finally get the car back after two weeks in the shop. The drive home from the shop is about 25 minutes of mostly highway, I immediately noticed on the on ramp it was a touch squirelly which was really strange considering all the bushings had been replaced and the car should feel tight as all hell. As soon as I get off the highway I decide to take it around my neighborhood and I hear the grinding noise. When load was transferred to the right side of the car I would hear a LOUD screech. At first I thought it was a bent brake dust shield or something rubbing on the rotor, but the screech was a little too loud and intermittent to really convince me that's what was wrong. Eventually, when I lifted the car up I happened to notice the back right wheel seemed to move A LOT as load was removed. Sure enough, I took a look around the back of the wheel and bearing grease is everywhere. I can move the wheel around quite a bit and my fear is realized.

Now, the subframe job is a big one, lot's of steps involved, and people can make mistakes. I'm thinking maybe they forgot to tighten one bolt, maybe used the wrong torque spec, something along those lines. Still, you send it to a trusted shop and pay that premium to avoid mistakes like that. Well... when I took the wheel off I quickly transitioned from annoyed but understanding to bewildered and disappointed. They had clearly punched out the indentation to remove the existing axle nut to do their work and then subsequently put it back on even though it was clearly broken. I took off the rear driver side wheel and sure enough, same thing, reused nut.

The axle nut is a $10 piece of hardware. ANY self respecting shop should be replacing these everytime they come off. In a shop that does as many BMW jobs as they do they should have a large box labeled AXLE NUTS to pick from. It's one thing if you're working on your own car and need to reuse it until you can get your hands on a new one, but this is a safety critical item. You indent the nut so that through the hot/cold cycles generated from braking and resting the nut which holds your axle on doesnt come loose. I have had a bearing blow on me at like 30 mph. You lose pretty much all control of your vehicle. At 60mph that can be deadly for you and anyone in the lanes next to you or oncoming traffic.

I called them yesterday when I realized the bearing was shot but before I realized why. They would like me to bring it in so they can work on it more.

What's everyones thoughts here? Am I misunderstanding something about the M3 axle nut that makes this ok? Should I let them touch my car ever again?

Here is an imgur link with some images

https://imgur.com/a/rOxbF2b

[oceansize]

If they removed the axle nuts they should have been replace no questions asked. Super dumb if what you say is true. Further why did they not just drop the rear end? It isn't difficult at all to simply drop the rear end and so I can't fathom why they even did what they did.

[Seagull]

I had them replace the subframe with a better condition one so they had to remove all that stuff

[FBloggs]

Judging by the close ups of the axle nuts, I don't see any tool marks on the sides of the nut(not shiny) and I see rust on the outer treads of the axle stub.
Has it been a while since the work was done? Because the nut looks untouched.
It is possible to swap the rear trailing arms with axles/bearings/ brake rotors intact to a different subframe or chassis even.

Disconnect:
Calipers,abs lines, brakeline/caliper from arm, pad wear sensor,inner cv joints ebrake cables from inside, headlite sensor, speedo sensor,,torquetube and drop the subframe,rear swaybar, upper and lower locating arms,springs diff and driveaxles and trailing arms as a unit.

But yeah, the axle nut have been reused once before, just doesn't seem to be recently.

[FBloggs]

Is the diff carrier obviously different? Did you keep the old one?

[oceansize]

I had them replace the subframe with a better condition one so they had to remove all that stuff

FYI: You don't need to remove any of that stuff to replace the subframe. You can drop the rear end as a unit disconnect the upper/lower control arms and a few bolts and the subframe will come right out.

[Seagull]

Maybe they didnt pull the axle? I'm hoping to get the complete picture here. I'm definitely bummed that the car was away for over two weeks and lots of $$ and now needs more work. I just dont see how you miss that axle nut even if you dont take it off. And just coincedentally it all falls apart the day I get it back?

Maybe they got a little spirited with the torch back there and melted a seal ?

[oceansize]

Maybe they didnt pull the axle? I'm hoping to get the complete picture here. I'm definitely bummed that the car was away for over two weeks and lots of $$ and now needs more work. I just dont see how you miss that axle nut even if you dont take it off. And just coincedentally it all falls apart the day I get it back?

Maybe they got a little spirited with the torch back there and melted a seal ?

I really can't believe a shop with experience in doing subframe jobs would do anything but drop the rear end as a unit, as you see in my picture, meaning there is zero reason to disassemble anything axle/hub/bearing related. I think you are jumping to conclusions about what occurred and you need to just ask the shop.

Edit: side note, it would have been good if they noticed stuff was wrong to inform you and most good shops would but.....

[Seagull]

I really can't believe a shop with experience in doing subframe jobs would do anything but drop the rear end as a unit, as you see in my picture, meaning there is zero reason to disassemble anything axle/hub/bearing related. I think you are jumping to conclusions about what occurred and you need to just ask the shop.

Edit: side note, it would have been good if they noticed stuff was wrong to inform you and most good shops would but.....

I agree they probably did drop the rear end as a unit. Obviously someone reused that axle nut (but as someone else pointed out it might not have been recent) and with all the work being done back there I made a presumptive connection between broken part in rear end and recent work done on rear end. The failure of the axle nut is clearly recent as you can see the fresh metal on the end of the shaft. Either way it is good to hear they probably didnt put that nut back on like that themselves.

To your point about noticing this, yes this should be glaringly obvious in the two weeks it was there or during the test drives. They noticed other less obvious things and we agreed to do some preventative work while they were in there.

[jbfrancis3]

Judging by the close ups of the axle nuts, I don't see any tool marks on the sides of the nut(not shiny) and I see rust on the outer treads of the axle stub.
Has it been a while since the work was done? Because the nut looks untouched.
It is possible to swap the rear trailing arms with axles/bearings/ brake rotors intact to a different subframe or chassis even.

Disconnect:
Calipers,abs lines, brakeline/caliper from arm, pad wear sensor,inner cv joints ebrake cables from inside, headlite sensor, speedo sensor,,torquetube and drop the subframe,rear swaybar, upper and lower locating arms,springs diff and driveaxles and trailing arms as a unit.

But yeah, the axle nut have been reused once before, just doesn't seem to be recently.

I completely agree on all points, and especially that they do not appear to have been removed recently. Since you mentioned performing maintenance otherwise, and I'm sure you've removed a wheel now and then, what were the condition of the nuts before bringing it in?

They wouldn't pull the axles. You don't need to as others have noted and it introduces a lot more time and effort, especially since the axle splines often fuse themselves to the hub splines. Also, they wouldn't simply replace the axle nuts just because of a visual queue: a primary rule of a job is don't go out of scope.

I hate to say it but based on what we've seen, I'm not drawing a connection between any of the 3 things highlighted: 1) subframe work 2) axle nuts and 3) bearing failure

You should remove a nut and check it yourself. You can even tap the end of the splined shaft and try to move it; I am betting you can wail on it and not get it to budge (don't wail on it unless you keep the nut threaded on the end, and hit the nut, not the shaft end). I'd even imagine you'll really struggle to get the nut off.

[Seagull]

I hate to say it but based on what we've seen, I'm not drawing a connection between any of the 3 things highlighted: 1) subframe work 2) axle nuts and 3) bearing failure

No, im relieved to hear that!! I hated imaging that this shop would do something so blatantly dangerous. Clearly something went wrong, but it's a relief to hear re-using an axle nut might not have been the reason. I'm going to go out and try to get a better look at the nut and check for tool marks etc

[Seagull]

Some more closeups of the nut...

[Sprp85]

As previous poster mentioned, highly doubt it is a recent take off & re-use; also, axle nuts should be replaced technically but I've seen cases where shops re-use them all the time without failures. Especially if you have enough surface to dent it in to act as a lock.

However, if they just simply swapped the hubs for whatever reason and the previous owner of the hub over torqued the nut, aka impact wrenching the hell out of it when installing, that will most likely lead to premature bearing failure.