Quick Trip => An Analysis

Matt Colie

Well-known member
Aug 15, 2008
11,101
807
113
South East Michigan near DTW
Ken et al,

As a guy that worked in Detroit in Durability, Validation and Warranty for a few decades, I should like to offer some opinions here. (In the words of
Dave Lenzi, if you can't measure it, it is an opinion.) That is what this will be. It just has some experience behind it that few people have had the
opportunity to get.

First, Ken, you didn't stand a chance.
I know you are thinking you might have done something to mitigate the damage, but no. Damage like that can happen well inside a human's capability to
recognize it and react. (Lots of very personal experience here.)

The good thing is that is all happened so fast that the transmission and torque converter could most likely absorb the impact without damage.

My scenario has the ring gear tooth chip as a result and not a cause. Something got in the ring and pinion gear mesh. Whatever it was real tough but
has probably been reduced to metal grains. If it has not, it is a big very flat chip of metal. It would not have to be big, but look for something
like a bearing cage that is missing a piece. You may never find it. This piece did three things that were not quite simultaneous:
It got into the mesh and locked up the ring and an pinion completely. Craig can tell you what the lash in the gear set is, but it is not much.
This jammed the ring over so hard that it cracked the housing.
When and while that happened the entire inertia of the coach was now on the drive axles. That was plenty to blow those semi-hard splines off. One
did probably break before the other. If I had parts in my hands, I could offer an opinion (there's that word again) as to which. But, it does not
matter as both were fatally wounded instantly. This is why the spider could not save one of them.
Now, the load was off the ring and pinion, then it could rotate to clear the jam that was the actual cause. After an entire event time of maybe a
quarter of a wheel rotation (based on disasters with instrumented vehicles) everything was done.

So, in the approximately 20 milliseconds that this all took place, you would have has no chance to sort out the separation of the events.

Fortunately, you and Elaine were not injured and the coach is at home and can be repaired.

Will we see you in Elkhart?

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit
 
Thanks for your opinion, Matt. Especially since it matches my own. :-)

Yes, we fully expect to be in Elkhart -- after GMCDL Noccalula Falls, AL
next Thursday, and "Save the GA Sun" in Dillard, GA on 21 Aug. Not gonna
let a little glitch like this slow me down!

Ken H.

> Ken et al,
>
> As a guy that worked in Detroit in Durability, Validation and Warranty for
> a few decades, I should like to offer some opinions here. (In the words of
> Dave Lenzi, if you can't measure it, it is an opinion.) That is what this
> will be. It just has some experience behind it that few people have had the
> opportunity to get.
>
​...
 
Matt, your scenario is consistent with what looks like brittle fracture.
Were it fatigue (from age), I'd expect some shiny areas on the fracture
surface. If it was a casting or hardening fault, I would expect some
evidence of a progressive failure, not what looks like an instantaneous
fracture.

Ken, you can have the 3.07 I left at your house to use as a core. I don't
think yours is going to be usable :)

So, do we put this in the category of freak failures that can't be avoided
by any specific maintenance action? If a failing bearing dropped a chip
that got caught between the ring and pinion, is there a way to prevent that
failing bearing beyond keeping up with the fluid? I'm looking for the
takeaway.

What amazes me more than anything is that the inner boots contained the
flailing axles after the splined sections broke off. Had they not, it would
have been worse.

Rick "better a failed half-shaft than a shattered transmission output
shaft" Denney

> Ken et al,
>
> As a guy that worked in Detroit in Durability, Validation and Warranty for
> a few decades, I should like to offer some opinions here. (In the words of
> Dave Lenzi, if you can't measure it, it is an opinion.) That is what this
> will be. It just has some experience behind it that few people have had the
> opportunity to get.
>
> First, Ken, you didn't stand a chance.
> I know you are thinking you might have done something to mitigate the
> damage, but no. Damage like that can happen well inside a human's
> capability to
> recognize it and react. (Lots of very personal experience here.)
>
> The good thing is that is all happened so fast that the transmission and
> torque converter could most likely absorb the impact without damage.
>
> My scenario has the ring gear tooth chip as a result and not a cause.
> Something got in the ring and pinion gear mesh. Whatever it was real tough
> but
> has probably been reduced to metal grains. If it has not, it is a big
> very flat chip of metal. It would not have to be big, but look for something
> like a bearing cage that is missing a piece. You may never find it. This
> piece did three things that were not quite simultaneous:
> It got into the mesh and locked up the ring and an pinion completely.
> Craig can tell you what the lash in the gear set is, but it is not much.
> This jammed the ring over so hard that it cracked the housing.
> When and while that happened the entire inertia of the coach was now on
> the drive axles. That was plenty to blow those semi-hard splines off. One
> did probably break before the other. If I had parts in my hands, I could
> offer an opinion (there's that word again) as to which. But, it does not
> matter as both were fatally wounded instantly. This is why the spider
> could not save one of them.
> Now, the load was off the ring and pinion, then it could rotate to clear
> the jam that was the actual cause. After an entire event time of maybe a
> quarter of a wheel rotation (based on disasters with instrumented
> vehicles) everything was done.
>
> So, in the approximately 20 milliseconds that this all took place, you
> would have has no chance to sort out the separation of the events.
>
> Fortunately, you and Elaine were not injured and the coach is at home and
> can be repaired.
>
> Will we see you in Elkhart?
>
> Matt
> --
> Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
> Electronically Controlled Quiet Engine Cooling Fan
> OE Rear Drum Brakes with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
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--
Rick Denney
73 x-Glacier 230 "Jaws"
Off-list email to rick at rickdenney dot com
 
> Matt, your scenario is consistent with what looks like brittle fracture.
> Were it fatigue (from age), I'd expect some shiny areas on the fracture surface. If it was a casting or hardening fault, I would expect some
> evidence of a progressive failure, not what looks like an instantaneous fracture.
>
>
> So, do we put this in the category of freak failures that can't be avoided by any specific maintenance action? If a failing bearing dropped a chip
> that got caught between the ring and pinion, is there a way to prevent that failing bearing beyond keeping up with the fluid? I'm looking for the
> takeaway.
>
>
> Rick "better a failed half-shaft than a shattered transmission output shaft" Denney

Rick,

After I wrote that I was thinking the same thing about a prevention.

I have no confidence that a magnetic fill plug would have a chance. The only possibility I could think of was to glue a magnet to the cover. As this
failure rare, I am not sure how much we can do to prevent it. Even if Ken had drained and refilled the gearcase the morning before, there is really
no way to protect for such an event. A big problem is that everything goes to Hell in a small number of milliseconds.

Matt
--
Matt & Mary Colie - '73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan
OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Twixt A2 and Detroit