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Old 3 Weeks Ago   #1
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So, what would cause.......

The castellated half shaft nut to shear off it's split pin, work its way off and then allow the half shaft, drum and wheel to come away...


Asking for a friend......
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Re: So, what would cause.......

POSSIBLY, if the nut wasn't done up tight enough, thus allowing free-play to build up in the hub which would work against the nut, and turn the nut enough to shear the split-pin. When the nut is done up to the point that the hub torque (pre-load) is correct, the nut is TIGHT, to a point that it would be difficult for it to undo and shear the correct size split-pin---was the correct size split-pin fitted?
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Re: So, what would cause.......

Quote Originally Posted by the hobbler View Post
POSSIBLY, if the nut wasn't done up tight enough, thus allowing free-play to build up in the hub which would work against the nut, and turn the nut enough to shear the split-pin. When the nut is done up to the point that the hub torque (pre-load) is correct, the nut is TIGHT, to a point that it would be difficult for it to undo and shear the correct size split-pin---was the correct size split-pin fitted?

I did consider the 'not tight enough' theory but due to the set up cant understand where enough force would be applied to turn the nut and shear the split pin especially when there is no turning forces against the nut as it is the splined coupler the nut tightens onto?....happy to be educated though if someone can explain.....
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Re: So, what would cause.......

Quote Originally Posted by the hobbler View Post
POSSIBLY, if the nut wasn't done up tight enough, thus allowing free-play to build up in the hub which would work against the nut, and turn the nut enough to shear the split-pin. When the nut is done up to the point that the hub torque (pre-load) is correct, the nut is TIGHT, to a point that it would be difficult for it to undo and shear the correct size split-pin---was the correct size split-pin fitted?
Seen that several times with Mini's...
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Old 2 Weeks Ago   #5
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Re: So, what would cause.......

Quote Originally Posted by The Whitakers View Post
....happy to be educated though if someone can explain.....
......I'd be happy to be educated too, but I missed too much skool.

I would carefully check that the rubber hasn't become detached from the "star" of aluminium carried on the driven hub spline. If it has, there could have been rotational movement which affected the big, dished, star-washer nder the castellated nut and that might cause it lo loosen.

I don't mean that I have ever seen this but just venturing it as a cause.
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Old 2 Weeks Ago   #6
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Re: So, what would cause.......

Quote Originally Posted by fiat500 View Post
......I'd be happy to be educated too, but I missed too much skool.

I would carefully check that the rubber hasn't become detached from the "star" of aluminium carried on the driven hub spline. If it has, there could have been rotational movement which affected the big, dished, star-washer nder the castellated nut and that might cause it lo loosen.

I don't mean that I have ever seen this but just venturing it as a cause.

I will check as I am awaiting to actually see the vehicle in detail to strip and get an understanding of what caused this (to me) catastrophic failure....


At the moment all I have is a wheel, drum and half shaft with stripped threads..
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Old 2 Weeks Ago   #7
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Re: So, what would cause.......

Quote Originally Posted by The Whitakers View Post

At the moment all I have is a wheel, drum and half shaft with stripped threads..

It can only get better from here...

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Re: So, what would cause.......

Quote Originally Posted by The Whitakers View Post
I will check as I am awaiting to actually see the vehicle in detail to strip and get an understanding of what caused this (to me) catastrophic failure....


At the moment all I have is a wheel, drum and half shaft with stripped threads..
I may have a spare axle 😀
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Re: So, what would cause.......

It happened on my Mini 1000 during one of the coldest nights in early 1980s. I think it had been over-tightened to align the split pin and the super cold put the metal into it's brittle phase. Thankfully mine broke while I was on a side street so no major harm done, but I had to buy a new CV joint at silly money.
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Re: So, what would cause.......

Quote Originally Posted by The Whitakers View Post
I will check as I am awaiting to actually see the vehicle in detail to strip and get an understanding of what caused this (to me) catastrophic failure...….


At the moment all I have is a wheel, drum and half shaft with stripped threads.…….
Some here have reported stripping the thread on the nut when trying to tighten it enough to get the collapsible spacer (fitted between the rear hub bearings in order to set end-float/pre-load) to start collapsing. Maybe a nut already so-damaged was used instead of being renewed? Perhaps someone thought it would be fine, the split pin would hold the nut in place...

If the remains of the sheared split pin are still in the hole in the halfshaft, you might be able to determine the direction in which the split pin was sheared - either by the nut rotating or, if the nut threads were damaged, by the nut being forced off axially. The metal of the split pin ends will usually be bent/wiped in the direction of the shearing force.

Al.
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Re: So, what would cause.......

Interesting to hear that some people have experienced the thread stripping off the stub-axle nut when trying to collapse the 'collapsible spacer'. I have found that there are 2 types of spacer being supplied, and one of them is so thick that it is almost impossible to collapse it. Some are a 'sort of gold' colour and the other is a more an 'aluminium'colour. If I remember correctly, the 'aluminium' coloured spacer is the easier to collapse---it looks VERY similar to the original factory items.
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Re: So, what would cause.......

Ok so I have seen the car now and can confirm the following....


The threads on the half shaft must have mullered there selves after the nut wound itself off as the threads in the nut are perfect. the split pin is still in the half shaft hole and it is hard to tell which way it sheared but given the threads in the nut are ok again the assumption is it wound itself off. The locating tab washer is a little battered and the 2 locating lugs are mullered. The aluminium/rubber coupling is fine albeit damaged on the exterior where it hit the road.


Ok a little more info. This is obviously my car, at the time of incident the car wasn't being driven it was actually on an 'A' frame being towed by myself behind our motorhome. It was early morning and due to little traffic and aid from google maps I dragged the poor little thing for 7.1 miles before I was alerted to the fact I had lost the wheel. I can hear you all cry, how the hell did you not realise! It is rather a large motor home and despite the missing wheel there was no extra noise or drag on the van. It has worn the back plate down to half and worn the bottom of the swing arm away...….luckily there is no further damage to the car just a little dent in ones pride...…


If I get chance I'll post some pictures but for now need to source some parts.
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Re: So, what would cause.......

Quote Originally Posted by The Whitakers View Post

Ok a little more info. This is obviously my car, at the time of incident the car wasn't being driven it was actually on an 'A' frame being towed by myself behind our motorhome. It was early morning and due to little traffic and aid from google maps I dragged the poor little thing for 7.1 miles before I was alerted to the fact I had lost the wheel. I can hear you all cry, how the hell did you not realise! It is rather a large motor home and despite the missing wheel there was no extra noise or drag on the van. It has worn the back plate down to half and worn the bottom of the swing arm away....luckily there is no further damage to the car just a little dent in ones pride...
I'm not normally prone to such abbreviations, but OMG

That must have been so upsetting. The best way to forget it is to fix it ASAP but take your time to get it right. And I wouldn't fall for the thought, "While I'm at it I might as well do a proper job," and end up with half the car stripped down and off the road for ages.

The towing aspect may give clues as to what caused it and my first thought is there may have been drag caused from the driveshafts; maybe the car was left in gear or somehow a gear became partially engaged?

In any case, once it's rebuilt properly I suspect this is a one-off, never likely to happen again...especially since you'll be driving it everywhere in future, won't you?
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Re: So, what would cause.......

Quote Originally Posted by fiat500 View Post
I'm not normally prone to such abbreviations, but OMG

That must have been so upsetting. The best way to forget it is to fix it ASAP but take your time to get it right. And I wouldn't fall for the thought, "While I'm at it I might as well do a proper job," and end up with half the car stripped down and off the road for ages.

The towing aspect may give clues as to what caused it and my first thought is there may have been drag caused from the driveshafts; maybe the car was left in gear or somehow a gear became partially engaged?

In any case, once it's rebuilt properly I suspect this is a one-off, never likely to happen again...especially since you'll be driving it everywhere in future, won't you?

Upsetting wasn't the word I was thinking off but yes I can admit I was upset about it all....


I thought about it been left in gear but the back wheels were deffo turning as we left the camping field and I would expect them to be locked up on the wet grass with the compression although this could not be guaranteed and I would have thought it would have bust the transmission or even the engine if it had been turning over?!?!


Its very strange but its safe to say I need a new offside swing arm, back plate and half shaft....
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Re: So, what would cause.......

Don't beat yourself up, could have been worse, a lot worse. No one got hurt.

A U.S. forum I post on, had a member who towed a fairly new Fiat 500 on an A frame behind his motorhome. He had accidentally knocked the 500 into 1st gear before setting off.....

I don't know what revs the poor little engine was forced to turn at on the highway but it must have been astronomical..... whether the timing belt snapped first or valve bounce caused the valves to hit the pistons, the outcome was the same > one ruined engine.

At least your engine is still ok (hopefully).

You've no way of knowing what was done to your car before you got it, could have been worked on my a charlatan - the only person I trust to work on my cars is an old guy called Al.

Al.
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