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Rear axle bolt failure...AGAIN!!

DcnPat

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It's a fair theory that on almost every one of these trucks that has a failed axle bolt, the other bolt is likely to fail at some point as well.

What's avoidable is waiting for it to fail. I don't understand why they don't replace both sides. Makes no sense. Even if they won't share exactly what they DO KNOW about the issue, they also know that the root cause affects BOTH bolts.

I can stomach the manufacturing flaw. It happens. But once the manufacturer identifies the problem and the solution, they have no defense for handling in such a manner.
I agree 100%. It seems to be every manufacturer these days. Jeep identified a problem.with the clock spring used in my 2016 Wrangler. Their solution was not to recall but give an extended warranty on just the clock spring. Sure enough, in the idle of supply chain issues my clock spring failed and the first replacement was bad too. They said there was 1 clock spring in the entire country available at the time. Took several visits and about 8 weeks to resolve. I pity anyone who had a failure after I got "the last one." The entire situation could have been avoided by a "customer satisfaction" program to replace the suspect parts years before they failed. They choose to gamble instead and the customer always looses in this situations.

Ford needs to step up and eat the $50 or so total cost per truck and just replace all the suspect bolts.
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bcb97

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ZDadofThree

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How does one know if the bolt shears. Is it a drivability issue, or is there something else to check?
 

jmargo

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I've no desire or basis for arguing any of the IMO good points raised above, and certainly don't want to come across as defending Ford's response to this issue.

Having said that, IMO one possible interpretation of the text in the pertinent CSP (attached) is that the current practice limits replacement to only failed axles in response to limited parts availability (hoarding to be able to address actual failures somewhat timely?).

Not at all suggesting that's (or any of this issue) a good situation, but it might be an understandable response at the moment (?).

I'm not affected (yet) and am keeping fingers crossed that eventually there will be an updated response by Ford that's more comprehensive and proven 'permanent'.

But hey, I'm an optimist by nature; so far my only solace is that Ford has at least finally and publicly acknowledged the situation by the issue of the CSP, so I'm running with that as an indication they're at least 'working the problem'.
Attachment II says if one side is bad replace both if I read it correctly.
 

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RidingHighNCO

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I've no desire or basis for arguing any of the IMO good points raised above, and certainly don't want to come across as defending Ford's response to this issue.

Having said that, IMO one possible interpretation of the text in the pertinent CSP (attached) is that the current practice limits replacement to only failed axles in response to limited parts availability (hoarding to be able to address actual failures somewhat timely?).

Not at all suggesting that's (or any of this issue) a good situation, but it might be an understandable response at the moment (?).

I'm not affected (yet) and am keeping fingers crossed that eventually there will be an updated response by Ford that's more comprehensive and proven 'permanent'.

But hey, I'm an optimist by nature; so far my only solace is that Ford has at least finally and publicly acknowledged the situation by the issue of the CSP, so I'm running with that as an indication they're at least 'working the problem'.
Thanks for the attachment, it included more into than I've been able to obtain from my dealer.
 

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RidingHighNCO

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What are the implications of continuing to drive if you are on a trip once the bolt breaks.
I don't know, I have not seen a cross-section of the hub assy but the dealer service department has stated that it is unsafe to drive. I really don't want to believe that a bolt is a single point failure resulting in an unsafe to drive vehicle but that is what I have been told.
 

amschind

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I'm so happy my cost benefit "analyst" on my Power Boost ruled out the Max Tow axle. Basically, all the extra $1k would get me was slightly larger brakes and a stronger bumper. Well it would have also gotten me a very problematic rear axle.
I was really bummed that circumstances prevented me from getting a Max Tow (wrecked car, out of town, last day on 0%). Now, after 2 years of "now I have an adjustable rear axle" threads, I'm thrilled that circumstances prevented me from getting a Max Tow.
 

Buyer2021

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How does one know if the bolt shears. Is it a drivability issue, or is there something else to check?
Take care lest you get 'flamed' - the word "shear" to describe this failure is a hot-button no-no for some forum pundits :ROFLMAO:
What are the implications of continuing to drive if you are on a trip once the bolt breaks.
FWIW, based on closely following many threads about this and study of the Workshop Manual .....
  • Most failures are discovered when folks have a rear wheel removed for whatever reason (tire rotation being common, for example)
  • The owner has no idea how long they've been driving with a broken bolt
  • The broken bolt/washer will be retained inside the center 'hubcap' of the wheel until the wheel (or the center logo cap) is removed
  • As mentioned, the easiest 'inspection' is to pop-off the logo center cap on the wheel and look inside
  • Sometimes the bolt tumbles inside that space and can be heard as clicking / tapping / rattling sound; sometimes it may wedge in one place and not tumble / not cause a noise
  • Often the broken bolt end is 'well-peened' (see the pic in post #25 above) indicating that it's been tumbling around in there for some time (a 'fresh break' will have some sharp edges at the very end of the break)
  • I've read a very few anecdotes (like ~3 out of well over 100) where the owner has suffered loss of driving force at the axle; those are cases where apparently many miles accumulated after the break and the axle shaft slowly migrated inboard from the hub until the splines disengaged or failed due to reduced engagement depth; none of these reported damage inside the differential as a result of that inboard migration. Otherwise, I've not seen any reports of drive-ability issues.
  • NOTE that the wheel is not retained by this bolt, nor is the brake rotor, nor does the brake rotor / caliper play a role in retaining the wheel even with the bolt broken. The wheel and brake rotor are retained by the hub flange which is integral to the hub itself, the hub being bolted to the axle housing by 4 bolts independent of the axle shaft.
  • NOTE too, that unlike all other current F150 axles, this unique 3/4-float axle assembly does not have a retaining circlip inside the differential which must be removed to extract the axle shaft; the complete assembly is removed / replaced without need to remove the differential cover
Attached FYI is the wheel hub R&R procedure which shows the 'assembly'; when the repair is done as specified in the CSP previously posted, the part number for the 'assembly' includes the axle shaft with the hub pre-installed on the shaft and bolted as a complete unit. The installing dealer does not need to press the hub on the axle shaft or install the end bolt, that's already done, they just pull out the complete assembly and re-insert the complete replacement assembly.

IMO this is a good procedure for the repair in that IF there has been any damage to the splined interface between the axle shaft and the hub, or IF there's any damage to the bearing(s) in the hub, that's all replaced as a pre-assembled unit provided to the dealer service tech.

Yes, to date the replacement assembly is the same PN and apparently the same parts as OE; so IF the failure was due to a 'bad batch' of out-of-spec parts, presumably the replacement is a cure; BUT IF the root cause is some deeper design flaw, at least for now that is not cured it seems. Ford has not explicitly publicly revealed the underlying cause of the failures to this point in time (if they even know that for certain themselves).

(there are of course countless posts by forum experts each claiming that they know the root cause of the failure and professing the certain solution ranging from different bolt-torque to installation of mega-strength bolts to total axle redesign; I guess ya gotta run with whatever makes ya feel good :cautious: )


FWIW here's my best effort at a schematic diagram of the subject axle main components
Ford F-150 Rear axle bolt failure...AGAIN!! 3-4 FLOAT SCHEMATIC DIAGRAM

NOTE - Ford considers the hub a 'non-serviceable' unit (to be replaced in its entirety if damaged) so the Workshop Manual reveals nothing about the internals / bearing(s) configuration within the hub.
 

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Snakebitten

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^^^
Another excellent summary of the entire subject. And although I have purchased the axle bolts and have them in the barn, I still haven't decided what I'd do with them.

Install them preemptively based on the theory of over torqued or inferior bolts in the batch?

Or wait and IF one broke, which I believe I would discover promptly because I fiddle with the truck continuously, then drill it out and replace the bolt before the spline had much time to work it's way in/out of hub.

Every day that has gone by and I have done nothing, probably reveals more about how I consider the issue. 🙃
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