F150 Powerboost Axle bolt sheared off

[UGADawg96]

UPDATE: Dealer just texted and said:

"Hello, we ordered rear axle shaft and bolt for you. It was ordered earlier and should be here on Monday."

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[UGADawg96]

Dropped off truck this morning. They gave me a Jan 21 built F150 King Ranch Ecoboost with 50k miles via the Enterprise location next door to them. Weird driving a short bed with no tow mirrors. First time seeing the full digital dash. Man those power steps are loud when they actuate.

Oh, and the auto start/stop is disruptive. Glad I have the PB. Silky smooth.

 

[Pedaldude]

UPDATE: Dealer just texted and said:

"Hello, we ordered rear axle shaft and bolt for you. It was ordered earlier and should be here on Monday."

If the axle shaft swap also entails swapping the hub; see if you can sweet talk the dealer into letting you have the old hub assembly.

So far, other than illustrations in the shop manual; there’s been scant information about the new 3/4 float hub and a sectioned or disassembled hub could fuel a few more pages of speculation on the various related threads

Good luck with your truck!

 

[tony72cutlass's']

Just for fun if we know the size and grade of bolt we could work out what the torque should actually be.

Then depending on whether it’s ‘oiled’ or not (with loctite) that’ll dictate the friction coefficient. The torque will not change, but the slipperiness of the fastener will affect the clamping force.

Fun fact about loctite is that it’s an anaerobic thread locker which means it only cures in the absence of air when threaded together.

 

[Snakebitten]

You fellas have way more engineering prowess than me, but I kinda wonder why if the bolt appears to be mostly tasked with keeping the splined axle shaft "located" appropriately in the hub, why does it require enough torque to even threaten the integrity of the bolt?
Or put another way, why wouldn't it be prudent to remove the factory bolt before it potentially breaks, and then replace it with less torque, but enough to hold the two objects securely?

Worst case scenario, you could monitor it for ever becoming loose, and then adjust the previous torque for trial #2.
The bolts are both affordable and available. Wouldn't a loose bolt that is noticed immediately and addressed be a better situation than broken bolts?

 

[Pedaldude]

The main problem is Ford tried to be cute and bring back a dead technology. We have no idea how much they “improved” it in this new 3/4 float axle, so it’s really just an internet circle jerk unless some real investigative efforts are made.

The only thing certain is that along the line between designing and executing the new axle: mistakes were made and Ford’s silence in the matter would suggest that they have no real solution for the mistake/s at this point.

As suggested here or elsewhere, it’s possible that the torque is to preload the bearing halves. However, if the other end of the axle is free to move, it’s really not able to do that.

If the bolt is only fastening the rotating bearing half to the axle, the splines should carry the radial forces but the axial forces in a true 3/4 float axle are carried by the axle shaft like in a semi-float design while vertical loads are carried by the wheel bearing bolted to the axle housing.

When using a bolt in tension, the torque is critical. Torque to yield, where the bolt actually stretches is needed to equalize the forces inside the bolt against the clamping pressure and in tension an under torqued bolt is nearly as likely to fail as an over torqued bolt in addition to not supplying the required clamping force to begin with.

Add to the clamping demand of the bolt that there is likely to be stress reversals from being twisted around by wheel/axle and it’s possible that it’s meeting with early failure due to plain old metal fatigue from being undersized.

Put your tinfoil hats on but remember when there were supply issues with the 3/4 float axle? It’s very possible to imagine that the issue was known even before the first production trucks hit the assembly line and they were unable to find a fix or alternative.

 

[Twg1]

Lost my second bolt today at 16k. First at 10k. Scratching my head on why this cheesy bolt was used. IRS/FWD drive axles have used a threaded axle and 36mm nut for years without issue. Unreal that this is the HD’ist axle you can spec on this truck and its so fragile.

 

[DT444T]

This is really making me want to buy two new bolts and install them, myself. I think Snakebitten did it. I'm 48k into my PB with max tow and haven't had one fail, yet. But it's sounding like it would be a LOT easier to just order the bolts and be done with it.

We have the technology.

 

[tony72cutlass's']

possible that it’s meeting with early failure due to plain old metal fatigue

I bet someone at Ford thought that using a TTY bolt would solve all their weird transient load problems since on paper they’re supposed to help reduce fatigue.

Or maybe they used this chart.. although I can’t seem to find a part number for Ford brand duct tape

 

[UGADawg96]

UPDATE: Dealer just texted and said:

"Hello, we ordered rear axle shaft and bolt for you. It was ordered earlier and should be here on Monday."

They texted that the repair has been completed and ready for pickup. If I can't get out of work early today, then I'll get it first thing in the morning.

 

[Snakebitten]

Love your attitude!

 

[UGADawg96]

Love your attitude!

 

[UGADawg96]

Got truck back this morning... so quiet now.

 

[excaliber]

Has this problem been rectified for vehicles that have not been built yet? Do we know that a 2023 truck with max towing package will have the same defective bolt installed or will they get ahead of this issue for new builds?

I called Ford today and asked the exact question. I got the typical run around and was told to call my local Ford dealer. I'm still waiting to see what happens with the 2023 max tow Powerboost's before I make any decisions on a new truck.

 

[Buyer2021]

FYI / FWIW, the latest tally of failures reported on 'the other forum'

Still nothing from Ford about the 'root cause' of the issue but perhaps noteworthy that there's no reports of failures on a truck with a documented build month after March 2022.

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