Max Tow Axle Bolt - Preventive measure?

[MEE0130]

I have a 2022 Powerboost (4500 miles) with max tow, and can’t count how many posts I’ve read about these bolts snapping. Luckily, I haven’t had it happen to mine at this point, but just waiting for the day to come. What I’m trying to avoid is being stranded without a vehicle for a lengthy period, while my local shop can’t get the parts to fix.

My question is, can I loosen the current bolts, and torque to the proper limit? I’ve read anywhere from 80 - 100 ft lbs. I’ve also read you can’t reuse the same bolt, so should I order some new ones, remove the originals, then use these, torqued to the proper limit? Basically - a bandaid approach until Ford comes out with a formal recall. Thanks for your help.

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[Je1279]

They are one time use torque to yeild bolts. You would need to remove them, replace them with new bolts and torque to spec. Were there any changes to the part number of the bolts between 2021 and 2022 due to the problem?

 

[tony72cutlass's']

Based on the type of failure I’ve seen (cup and cone) the plane of failure is likely axial

I’m thinking you’re better off to wait for a new bolt grade or something because replacing it might just get you back to square 1.

This is just an impartial 2 cents since I don’t have max tow!

 

[tony72cutlass's']

They are one time torque bolts. You would need to remove them, replace them with new bolts and torque to spec. Were there any changes to the part number of the bolts between 2021 and 2022 due to the shearing problem?

Interesting it could be shear maybe I’m looking at it wrong. Very weird failure for this mature of a truck IMO

 

[Je1279]

Interesting it could be shear maybe I’m looking at it wrong. Very weird failure for this mature of a truck IMO

Tensile failure (or cup and cone fracture as you stated) is a better description. Below is what the bolts typically look like afterwards for those unfamiliar.

 

[tony72cutlass's']

Tensile failure (or cup and cone fracture as you stated) is a better description. Below is what the bolts typically look like afterwards for those unfamiliar.

Wow that’s a great image showing the failure, any idea what causes it?

 

[RossRR]

Interesting it could be shear maybe I’m looking at it wrong. Very weird failure for this mature of a truck IMO

The truck may be mature but the axle is a brand new design introduced for 2021 max tow vehicles.

 

[Buyer2021]

My question is, can I loosen the current bolts, and torque to the proper limit? I’ve read anywhere from 80 - 100 ft lbs. I’ve also read you can’t reuse the same bolt, so should I order some new ones, remove the originals, then use these, torqued to the proper limit?

Just FYI and FWIW, here's the pertinent bolt installation text clipped from the Ford Workshop Manual as of 08/12/2022:

NOTE: Make sure a new bolt is installed.​

Install the washer and tighten the bolt.​

Torque :​

Stage 1: 52 lb.ft (70 Nm)​

Stage 2: 90°​

 

[MEE0130]

Just FYI and FWIW, here's the pertinent bolt installation text clipped from the Ford Workshop Manual as of 08/12/2022:

NOTE: Make sure a new bolt is installed.​

Install the washer and tighten the bolt.​

Torque :​

Stage 1: 52 lb.ft (70 Nm)​

Stage 2: 90°​

Good to know. I have some new bolts ordered. Just so I know, are the current original bolts over torqued, which contribute to them breaking?

I’m just curious to see if this replacement process with proper torque values will “prolong” their life compared to current.

 

[Buyer2021]

Just so I know, are the current original bolts over torqued, which contribute to them breaking?

No One Knows . Speculation and opinion are rampant but AFAIK there is no method to determine the installation torque of a torque-to-yield fastener after it has been installed.

Just for consideration ... while it's possible that the bolts were over-torqued and that contributed to failure, IMO it's also possible that they were torqued properly but then movement of the axle shaft relative to the splined wheel hub assembly contributed to the failure. That 'movement' may be of a type that is relatively independent of the fastener torque or 'strength' (e.g. 'wiggle' within a 'sloppy' splined interface). That's only one of many theories which have been advanced and may be within the realm of possibility.

I’m just curious to see if this replacement process with proper torque values will “prolong” their life compared to current.

FWIW there has been at least one report of a dealer-replaced bolt (without axle replacement) failing. Who knows if that replacement was was installed to the proper torque spec?

Note that the Workshop Manual procedure for calls for installing the hub to the axle shaft with a hydraulic press to 'seat it' against a washer retained on a lip of the axle shaft on the inboard side of the hub. IF, for whatever reason, the hub is no longer fully 'seated' on the axle shaft (i.e. the axle shaft has 'slid inboard' relative to the hub), then replacement and proper torque-ing of the bolt may not remedy that.

I suppose an argument can be made that IF your bolt is 'on its way' to failing then a replacement would defer the occurrence.

I guess ya gotta go with whatever makes ya feel good.

 

[Atlee]

No One Knows . Speculation and opinion are rampant but AFAIK there is no method to determine the installation torque of a torque-to-yield fastener after it has been installed.

Question you may know the answer to, or not. And the answer is just for my education.

Why were "torque to yield" bolts invented in the first place. Why is superior to use one of those rather than a high quality reusable bolt?

 

[Je1279]

Here is an article I found that provides a good overview.

https://www.counterman.com/torque-t...theyre-used-and-why-they-need-to-be-replaced/

 

[tony72cutlass's']

Once upon a time someone told me that it increases the fatigue life of the fastener with the high clamp you get

 

[Buyer2021]

Question you may know the answer to, or not. And the answer is just for my education.

Why were "torque to yield" bolts invented in the first place. Why is superior to use one of those rather than a high quality reusable bolt?

To your good question I've nothing to add to the info in the article linked by @Je1279 (google will reveal other articles offering explanations in more or less technical terms and more or less depth / detail).

 

[Porpoise Hork]

Good to know. I have some new bolts ordered. Just so I know, are the current original bolts over torqued, which contribute to them breaking?

I’m just curious to see if this replacement process with proper torque values will “prolong” their life compared to current.

I replaced mine a couple weekends back out of precaution. Took no time at all to do it. One thing I wanted to know was what the final torque was on these. I set the wrench to 52 and then incrementally increased 10 ft.lbs at a time while continuing to the 90 degree turn. Final torque ended up at 120. Not sure what long term impact doing this will be but at least I know they are now at the recommended torque.

Probably not a bad idea to have a spare set lying around so if one snaps I can drill it and pull it out to replace it.

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