Diff Pinion Flange Dropped Off

Apparently, the split pin was so corroded that it fell out of both the castellated nut and the pinion, which stripped the threads out of the nut.
The two remnants of the split pin show no signs of corrosion, and the only bits to be found were the ends of the 'legs, with the 'bulb' part and the legs through the pinion missing.
Can anyone recommend an independent engineer/metallurgist to give a professional, unbiased opinion?

Looks to me like that nut was already stripped when fitted and has pulled of the pinion shaft threads as they aren't damaged. I'd have expected both the nut and shaft threads to be stripped if the pinion flange dropped off. Who says that the split pin failed?

split pin condition is irrelevant,nut hasnt just undone due to split pin failing.that nuts been over tightened or props slide is seized and its been pulled off slide hammer style over a little time

Thanks for that @jamesmartin. I hadn't considered that possibility!
They have had the propshaft off to change the gearbox, and would surely have noticed had it been siezed either when removing or refitting it!
Had the propshaft siezed earlier, the only other time it was off was during the chassis change, a couple of thousand miles ago, when noting amiss was noticed either.
Is this down to incompetence on their part, I wonder??

I also think a duff already damaged nut was fitted at some time and things only came apart when the split pin gave up having taken a battering for some time from the loose nut.

Often spit pins ars reused which weakens them having being bent then straightened then rebent, and if this has been done twice or more the split pin could easily snap, looking at the photo of the remains of the spit pin it looks like this is what has happened. They should really only be used once then discarded.
The nut may also have had a damaged thread when put back on.

It would appear that our Guru, Sir @jamesmartin is quite correct, as I went down and took a few more pics yesterday, and sure enough, the propshaft was siezed up solid!
As I have only done a few hundred miles since getting her back from a gear and transfer box rebuild (by Ashcrofts,) is it possible for the shaft to sieze up in such a short time, or would it be quite obvious to whoever removed and refitted it that something was not quite right with it, making it difficult to replace?
Historically, both of the propshafts tended to be greased annually, which is why am am amazed that he front one was siezed, unless overtightening the collar might have had any affect on it?
Would the garage be responsible under a duty of care to inform me that the shaft was siezed solid?
The half shafts didn't asppear to be too badly damaged, and I think that that can be mainly attributed to wear.
A couple of further pics to be going on with, and your views and comments would be very much appreciated. ...

That the diff pinion threads escaped with no visible damage is interesting, guess it is a lot harder than the nut. Halfshaft wear looks normal.

I have arranged for an independent inspection of the propshaft and diff as per the garages' suggestion, and now they suddenly say that 'it's not convenient' because, even though the premises will still be open, their Ops Director is on holiday!
Can they refuse access?

Do not see why you and anyone you want can not go and take a look. It is your truck after all .

I assume that they want access to the inspector without him having any chance of discussing the issues with me first, thus allowing them to present their excuses uncontested.

Which Axle is it Mate ? Ive got a coupe of decent half shafts, if there the same your welcome to them.

border said:

Which Axle is it Mate ? Ive got a coupe of decent half shafts, if there the same your welcome to them.

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Thanks for the offer @border It's the front axle, and the independent examiner will be looking at it today.
The Motor Vehicle Apprentice Training Garage has spent the past week trying to prevent me from getting access, and they have made it clear that they don't want me around today!
I wonder what they have got to hide ???
They can think again, because I will be there!

They are now saying that the pinion detached due to a lack of maintenance and wear and tear on the pinion trrust bearings.
I might be being a bit of a dipstick here, but wouldn't it be just a slightly bit obvious that any linear or radial free play on the pinion flange would be picked up when the propshaft was removed and refitted?
Over the past 3 years they have had her more that I have, starting with the chassis swap over (9 months), then the sudden failure of the gearbox last year (lost drive with no warning whatsoever), they had her almost 6 months, and now another almost 2 months to strip the front diff after the catastrophic failure of the drive.
Is it down to either ignorance or total inompetence that the issue was not spotted and reported on?

Oldseadog said:

They are now saying that the pinion detached due to a lack of maintenance and wear and tear on the pinion trrust bearings.
I might be being a bit of a dipstick here, but wouldn't it be just a slightly bit obvious that any linear or radial free play on the pinion flange would be picked up when the propshaft was removed and refitted?
Over the past 3 years they have had her more that I have, starting with the chassis swap over (9 months), then the sudden failure of the gearbox last year (lost drive with no warning whatsoever), they had her almost 6 months, and now another almost 2 months to strip the front diff after the catastrophic failure of the drive.
Is it down to either ignorance or total inompetence that the issue was not spotted and reported on?

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So, do you have mostly apprentices working on it?

Cheers

I don't know. However, the instructor should have checked everything if the works were carried out by an apprentice, and the training organisation is responsible for any errors resulting from a lack of guidance and tuition.
Just as a matter of interest, don't the propshafts get wiggled during the MoT inspection as the drive train and UJ's form a part of the test, and probably could generate at least an 'Advisory'?

Oldseadog said:

I don't know. However, the instructor should have checked everything if the works were carried out by an apprentice, and the training organisation is responsible for any errors resulting from alack of guidance and tuition.

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You would hope so.

Cheers

Oldseadog said:

They are now saying that the pinion detached due to a lack of maintenance and wear and tear on the pinion trrust bearings.
I might be being a bit of a dipstick here, but wouldn't it be just a slightly bit obvious that any linear or radial free play on the pinion flange would be picked up when the propshaft was removed and refitted?
Over the past 3 years they have had her more that I have, starting with the chassis swap over (9 months), then the sudden failure of the gearbox last year (lost drive with no warning whatsoever), they had her almost 6 months, and now another almost 2 months to strip the front diff after the catastrophic failure of the drive.
Is it down to either ignorance or total inompetence that the issue was not spotted and reported on?

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Why do you keep taking it there for repairs

The chassis is a simple job, the I was supposed to have witnessed the gearbox bewing opened, as I might have been able to see what went wrong internally, and the pinion due to not having driven more than a few hundred miles since the gearbox was replaced, it was evident to me that they they had a continuing duty of care, and legally they must be given the opportunity to rectify any faults arising from their works.
Apart from which, I was involved in an RTA in January 2017, which resulted in having my left wrist rebuilt four times, along with operations on my shoulder and ankle, which rendered me rather incapable of carrying out the works myself. Fortunately, I am regaining some of the strength, and have managed to achieve around 70% of the articulation of my arm.

Oldseadog said:

They are now saying that the pinion detached due to a lack of maintenance and wear and tear on the pinion trrust bearings.
I might be being a bit of a dipstick here, but wouldn't it be just a slightly bit obvious that any linear or radial free play on the pinion flange would be picked up when the propshaft was removed and refitted?
Over the past 3 years they have had her more that I have, starting with the chassis swap over (9 months), then the sudden failure of the gearbox last year (lost drive with no warning whatsoever), they had her almost 6 months, and now another almost 2 months to strip the front diff after the catastrophic failure of the drive.
Is it down to either ignorance or total inompetence that the issue was not spotted and reported on?

Click to expand...

pinion bearing failure rarely results in flange nut been stripped off , if prop slide was seized thats the cause