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Can anyone tell me what this is (part failure on axle)......?

Pedaldude

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There’s a member here who ponied up for the shop manual. I’ll send him a message. The only thing is; that if it’s a design flaw, it might not do any good to bother and if it’s a supplier issue and they are still using the same bolts, it still won’t matter. Or if it was only a problem impacting certain builds, you might not need to worry.

Unless people share at the very least their truck’s build date and mileage at failure, only Ford has a decent idea of what’s going on.

The only variable that I can think of at this moment that would be eliminated by swapping out the bolt is incorrect torque while perhaps also resetting your miles to failure but then again some people are having the failure at pretty low mileage and others as far as I know aren’t having the failure with many hard miles. So you’re potentially setting yourself up for failure by swapping the bolt, which might be why Ford hasn’t done anything so far. o_O

Here’s a thread discussing the failure on PB trucks:

https://www.f150gen14.com/forum/threads/f150-powerboost-axle-bolt-sheared-off.10392/

and on the other f150 forum, there’s a thread titled: 2021 Powerboost Rear Rotor/Axle Bolt Sheared

Both contain additional speculation and information, one mentions 111 passenger side axles on backorder and a report of a driver’s side bolt failing. There’s even a mention of there being a TSB but then there’s also plenty of instances of owners being gaslighted by their dealers.
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The bolt is not to be re-used according to my shop manual. (see attached PDF)
Wheel Hub Install:
1. Install the inboard washer.
2. Using general equipment, press the wheel hub assembly onto the axle shaft. Use the General Equipment: Hydraulic Press
3. NOTE: Make sure a new bolt is installed.
Install the washer and tighten the bolt.
Torque : 100 lb.ft (135 Nm)

The wheel hub base is then held on by the 4 bolts in the attached picture:
Ford F-150 Can anyone tell me what this is (part failure on axle)......? holding base.JPG

How is the rotating assembly retained without the outer wheel hub bolt?
 

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Pedaldude

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Ford F-150 Can anyone tell me what this is (part failure on axle)......? C3A4CDBB-ABBF-4FAC-B213-4A283AC67A1F


With this image, pretending that the axle was held on by a missing bolt; only the friction between the splines, the bearing races/seals and the brake calipers are holding the wheel on in a turn or when on a transverse incline.

This is not a diagram of Ford’s hub assembly, so it could be something entirely different.

One of the things that I notice is that at least in Ford’s exploded parts diagram; the 3/4 floating axle doesn’t have an axle retaining clip like the regular 9.75” axle does. Which would mean that if the physical axle matches the diagram, that even with the bolt intact, there’s still nothing holding the rotating assembly in the axial direction and that categorizing the axle as a traditional 3/4 floating is incorrect and that while not being a traditional full floating it could be more like the bolt on wheel hubs that FWD vehicles have on the rear axle. In which case the tiny axle bolt’s only purpose is to locate the axle within the axle housing assembly. I don’t know! Is it really a 7/8 floating axle? Was the bolt superfluous and added as an afterthought because of a non-engineer who just couldn’t handle the thought. Some owners think that they have driven hundreds, if not thousands of miles with the axle bolt sheared off. Though if there’s no stress on the bolt it shouldn’t be breaking. I have more questions than answers now.

Until someone disassembles the hub or sections it in half, I have nothing but guesses at this point.

Ford F-150 Can anyone tell me what this is (part failure on axle)......? A8029479-B83F-4A91-9700-E5600A0CE448


Ford F-150 Can anyone tell me what this is (part failure on axle)......? 0F2C1665-5E43-4BF9-A190-1D5EAF4C4A9A


Above is the standard axle assembly with the grooved axle and also the axle retaining clip, c-clip or axle retainer that keeps it in place.
 

tc429

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C3A4CDBB-ABBF-4FAC-B213-4A283AC67A1F.jpeg


With this image, pretending that the axle was held on by a missing bolt; only the friction between the splines, the bearing races/seals and the brake calipers are holding the wheel on in a turn or when on a transverse incline.

This is not a diagram of Ford’s hub assembly, so it could be something entirely different.

One of the things that I notice is that at least in Ford’s exploded parts diagram; the 3/4 floating axle doesn’t have an axle retaining clip like the regular 9.75” axle does. Which would mean that if the physical axle matches the diagram, that even with the bolt intact, there’s still nothing holding the rotating assembly in the axial direction and that categorizing the axle as a traditional 3/4 floating is incorrect and that while not being a traditional full floating it could be more like the bolt on wheel hubs that FWD vehicles have on the rear axle. In which case the tiny axle bolt’s only purpose is to locate the axle within the axle housing assembly. I don’t know! Is it really a 7/8 floating axle? Was the bolt superfluous and added as an afterthought because of a non-engineer who just couldn’t handle the thought. Some owners think that they have driven hundreds, if not thousands of miles with the axle bolt sheared off. Though if there’s no stress on the bolt it shouldn’t be breaking. I have more questions than answers now.

Until someone disassembles the hub or sections it in half, I have nothing but guesses at this point.

A8029479-B83F-4A91-9700-E5600A0CE448.jpeg


0F2C1665-5E43-4BF9-A190-1D5EAF4C4A9A.jpeg


Above is the standard axle assembly with the grooved axle and also the axle retaining clip, c-clip or axle retainer that keeps it in place.
as there were a couple photos with oil puked out all over brakes/wheel, there must be nothing but press fits holding the thing together if that bolt is missing. odd thing- a straight/press fit spline seems odd, tolerance would have to be very critical- not only on diameters, but also the tooth form. I'm certain they still use pull broaches for hub splines- about the only way to produce- and almost certain a Marand spline roller or similar would be used to spline the axles... we ran slip yokes and splined shafts at work for hydramatic div of GM for years, and its hard to beat the repeatability of the broackes/marand roll spline equipment- but they both rely on broach bars and roll blocks ground with the involute tooth form being very precisely controlled... as they are pressing into a bearing equipped hub, press fit could likely not be much over .001 to prevent stretching inner bearing ring/increasing bearing preload... all the male s;lines we made, also went directly from the spline roller to induction heat treat- high frequency turns part bright red while underwater- which shrunk the shaft a little, then a slow moving draw/age furnace to reduce hardness... what seems odd to me is the 'general press' equipment comment- no mention of any lubricant being applied... clean, stiction/galling can remove metal friction welding parts together, not fully seated even after bolted... bump a curb(passenger side) knock the hub further on/bolt now loose...things start walking... anyways agree- till we see a cut hub its all bench racing... hope they figure it out soon- for now just glad mine has the older style axle in it
 

tc429

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The bolt is not to be re-used according to my shop manual. (see attached PDF)
Wheel Hub Install:
1. Install the inboard washer.
2. Using general equipment, press the wheel hub assembly onto the axle shaft. Use the General Equipment: Hydraulic Press
3. NOTE: Make sure a new bolt is installed.
Install the washer and tighten the bolt.
Torque : 100 lb.ft (135 Nm)

The wheel hub base is then held on by the 4 bolts in the attached picture:
holding base.JPG

How is the rotating assembly retained without the outer wheel hub bolt?
notabot- thanks for the info- question: does the axle removal procedure start out by pulling pumpkin open/removing c clips? I agree with pedaldude, it seems this must be the case else it wouldnt matter if bolted or not...would be a point to confirm while pondering over...
 

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Pedaldude

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While the axle and axle housing illustrated in the procedure is the conventional semi-float, I did find an image of the retaining clip in the differential section.

Searching my VIN in parts.ford brought nothing related up but the axle retaining washer is likely there.

Which brings everything back to that little bolt being the only thing holding the wheel on after the brake caliper.

Ford F-150 Can anyone tell me what this is (part failure on axle)......? 82E79460-69E7-4AFF-84D5-D9116BAF680B
Ford F-150 Can anyone tell me what this is (part failure on axle)......? 48317C8E-94A7-4329-82AD-8FF7479E4464
 

tc429

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Retaining washer... See attached
thank you- so it is retained like a standard 8.8/other common axles...good to know for certain that that bolt(and the press fit) are all holding the hub from moving outward axially...think everyone assumed this to be the case, great to know for sure :)
 

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To add to the amount affected, I too had one of these bolts shear off the rear passenger wheel assembly. Had been hearing a rattling noise from that area so had a local shop check it out. Sure enough the top end of the bolt was sitting there captured by the wheel from falling out. Its been two months since my last oil change and tire rotation so hard to say how long I'd been driving it like that.
The dealer looked at it yesterday and sure enough put in an order for a new axle which is on backorder, no ETA at the moment. They had never seen one before but looked online at forums and saw these discussions. They told me its safe to drive until the axle comes in but I'm not so sure.
For reference, I've got a 2021 3.5EB XLT with the max tow package and 3.55 ratio. I filed a complaint with the NHTSA.
 

Pedaldude

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I wouldn’t be driving around without it, at least not anywhere other than to the dealership when they get the parts.

As above, the only thing other than the bolt holding the hub on is the friction between the splines and the brake caliper mount. While the brake caliper mount bolts kinda are supposed to be able to share the force, since nothing is completely rigid; they’re really only supposed to be handling the braking torque in shear and not holding the hub to the axle. It’s common enough for wheels to fall off when axles break, that there are off-road compilation videos of it happening on YouTube. While I think it’s mainly with drum brakes, I have seen it happen in person where a lifted Jeep Wrangler with giant tires tripped over its front wheel after the axle broke and tore the disc off along with the wheel while making a slow speed turn.

How many miles does your truck have and did your dealer’s service department try to remove the broken bolt half stuck in the axle?
 

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tc429

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While the axle and axle housing illustrated in the procedure is the conventional semi-float, I did find an image of the retaining clip in the differential section.

Searching my VIN in parts.ford brought nothing related up but the axle retaining washer is likely there.

Which brings everything back to that little bolt being the only thing holding the wheel on after the brake caliper.

82E79460-69E7-4AFF-84D5-D9116BAF680B.jpeg
48317C8E-94A7-4329-82AD-8FF7479E4464.jpeg
yep- does seem a little light huh...look at the nut/thread diameter on a escort/other front hub... sure seems like ford went light on this. Aad thing is, the old full floater design with the bolted in axles had been around/trie-and-true forever...two tapered roller bearings to locate axially and handle all radial/thrust/moment loading scenarios...but a single radial only ball is cheaper... I got a feeling this 'economically driven' design is gonna be expensive... bean counters costing money over trying to be cheap :(
To add to the amount affected, I too had one of these bolts shear off the rear passenger wheel assembly. Had been hearing a rattling noise from that area so had a local shop check it out. Sure enough the top end of the bolt was sitting there captured by the wheel from falling out. Its been two months since my last oil change and tire rotation so hard to say how long I'd been driving it like that.
The dealer looked at it yesterday and sure enough put in an order for a new axle which is on backorder, no ETA at the moment. They had never seen one before but looked online at forums and saw these discussions. They told me its safe to drive until the axle comes in but I'm not so sure.
For reference, I've got a 2021 3.5EB XLT with the max tow package and 3.55 ratio. I filed a complaint with the NHTSA.
glad you filed NHTSA...heard theyve got like 1100, so Fords gonna have to be getting pressure on this- the sooner the better. TSBs till out of warranty is all too common- I can about guarantee theres noisy tire shops that found bolts on the ground that went unnoticed when they fell out... time will tell. anyone seen anything on a redesign? heavier bolt? maybe they'll have dealer techs weld tem up like the thin tubes on sperduties that were flattening out... just kidding- but it is kinda sad that tried and true things were 'updated' into problem child things... that thing with them having dealer techs weld to add thickness on those superduty axle housings that were too thin/dented at full load causing axles to roll ripping driveshat/brakelines off if throttled hard fully loaded, still makes me scratch my head... how this underrated stuff ever passed engineering seems odd- big bucks to tool up- much bigger bucks to redesign/replace... oddly its been more 'simple' things with ford than complex... very advanced on every level, then they make a thin axle tube to save eweight, or use a small bolt/single bearing to save weight/money, or go back- unpainted widstar chassis parts cost them 5 billion in recalls, all the 5.4/4.6 2vs with like 3 threads on spark plug that stripped after changing, or the 3v 4.6 with the friction welded shell that wrings off in the head when removing... all oems have issues, but when its simple stuff that at a glance 'dont look right', gotta wonder if they might be a bit too light on the engineering staff who decides service factor ratings/verifying designs exceed minimums by a reasonable margin....
 

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I wouldn’t be driving around without it, at least not anywhere other than to the dealership when they get the parts.

As above, the only thing other than the bolt holding the hub on is the friction between the splines and the brake caliper mount. While the brake caliper mount bolts kinda are supposed to be able to share the force, since nothing is completely rigid; they’re really only supposed to be handling the braking torque in shear and not holding the hub to the axle. It’s common enough for wheels to fall off when axles break, that there are off-road compilation videos of it happening on YouTube. While I think it’s mainly with drum brakes, I have seen it happen in person where a lifted Jeep Wrangler with giant tires tripped over its front wheel after the axle broke and tore the disc off along with the wheel while making a slow speed turn.

How many miles does your truck have and did your dealer’s service department try to remove the broken bolt half stuck in the axle?
That's what I figured, I drove it home last night because I didn't want it sitting at the dealer lot but its going to stay parked until the replacement arrives. When they say "axle", does that mean they're replacing the entire axle or just the spindle and hub? Seems like that's all that would be needed but I'm guessing it comes as a unit from Ford.

I've got just under 25k miles, 95% highway as I drive a lot for work. I don't believe they tried to take out the broken piece but I didn't ask and haven't taken the wheel off to check. Thought about taking it out myself and putting in a new bolt until the axle comes so I can drive my truck but I probably wont end up doing that.
 

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no no no...pic of the lifted 2020 STX loaner.
Well I appreciate the pic of the problem! Thank You. It would certainly be unsafe to drive this around with the hub retainer missing.
 

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