Stelvio 1200 - broken gearbox output shaft

[guzzdi]

When I was riding steep uphill on forest road, my bike suddenly lost traction. The engine worked fine, but no power goes to rear wheel on any of gears. Clearly major failure in a middle of nowhere :)
I called friends with off road trailer and we succeed to evacuate the bike.
At home we started to diagnose and first thought about failed clutch or final drive. We took out final drive (just as it’s easier) and realized that cardan shaft is not spinning (with engine running in a gear). We took out cardan and to the biggest surprise found the problem - the very end of gearbox output shaft broke from the gear shaft. Like somebody cut it wit a laser!!
I never experienced or saw something like that on any motorcycle in my life (I owned 6-7 during many years).
Did anybody hear or read about such failures and any reason (besides manufacturing defect) it may happen?
I’m thinking that replacing whole gearbox (but used on eBay?) is the best possible option. The alternative is to search for output shaft only and take apart gear box which sounds scary to the degree and probably not much cheaper at the end.
Any collective thoughts?
And the question - are gearboxes all same/identical for different years Stelvio 1200 4V? What about identicality between 4V 8V NTX etc? Just want to be sure which one to look on eBay.
Thx
Attached pictures of the broken part

[lucian]

Damn . I would say Moto Guzzi owes you a new shaft. I would contact them . It must be a manufacturing defect.

[Muzz]

See p.m.

[guzzdi]

See p.m.

Thx, got it, replied

[guzzdi]

Damn . I would say Moto Guzzi owes you a new shaft. I would contact them . It must be a manufacturing defect.

The bike is Stelvio 1200 4V 2008.
I really doubt they will treat as "manufacturing defect" (though it really is)
Unless there is a good contact somewhere in corporate who can provide an exception authorization for parts and work to the local dealer/service center to fix it :)

[tris]

I'd  love to put that in the hands of one of our metallurgists and see if they could identify the failure mode.

If a lab inspection is a possibility, don't  touch the fracture surface and don't put it back on the remains of the shaft. They can tell loads by just looking under a microscope

It could be a manufacturing defect,  but might be something else entirely.

[guzzdi]

Tris,

I don’t have here in Seattle access to such level metallurgists :)
Besides that, I cannot even imagine what are possible any other reasons except manufacturing defect? I was single on a bike, going uphill gravel road, no luggage, on a second gear about 20 km/h.
Uphill steep, but I wouldn’t think of it as something extraordinary from a bike load perspective.
And what is a point to “prove” manufacturing defect? The bike is out of warranty anyhow…

Cheers

[tris]

Just idle curiosity,  as its an unexpected failure, and  us Mech Es are curious about such things

But, I agree, wouldn't change anything.

[guzzdi]

Hello,

Just wanted to provide an update.
With the help of Muzz and his friend, I was able to handle it in a proper way - replacing the gearbox with a broken output shaft with the used gearbox.
Not an easy, but very challenging and interesting task.
First, had to remove the engine with gearbox from a bike, or more accurately would probably say "remove the bike from and engine" :)
Some pictures:





Now ready to remove the engine:



2018 brz 0 60


And separate gearbox from the engine:






and put the "new" (used) gearbox back on the engine - I put a small broken part of output shaft next to the "new" output shaft of gearbox for comparison and show where it belonged:




And put everything back on the bike:









Out of curiosity, I disassembled old gearbox completely, so wanted to show all components of this piece of enegineering:






And here is the failed part to blame fro all this work - output shaft with a broken piece. If somebody wanted to examine it metallurgically to find "why it broke" - just pay shipment and and I can ship 



geojson spec


To summarize - challenging, but doable task of replacing a gearbox. The hardest part of the job is to remove engine from the bike - I put a bike jack with large flat surface on top under the engine and pulled the bike slowly up maneuvering through the frame structure.
Using the opportunity, I also checked all swingarm, wishbone, etc bearings. Thankfully they were not "deserted" like in some pictures I saw on this forum, so I just cleaned, re-greased and put it all back.
The bike is running great!

Thanks all who helped with advises.
Safe rides!

[guzzisteve]

How was that breather plate on front cover left side? Hang you up? PIA every time I do one. Book pays around 10hrs.

[guzzdi]

This one #2



Or which plate do you mean?

[tris]

 

And here is the failed part to blame fro all this work - output shaft with a broken piece. If somebody wanted to examine it metallurgically to find "why it broke" - just pay shipment and and I can ship 



geojson spec

If you can get a couple of good pictures of both the fracture surfaces I can show them to one of our metallurgists

Can't do the lab work, but obvious stuff they'll spot and interpret from the pictures

[guzzisteve]

This one #2



Or which plate do you mean?

No, the cover plate over square hole on LH side of front timing chest. Behind the LH upper frame mount.
2V models have a breather hose going there.

[Muzz]

Good to see you got it all sussed Guzzdi.

Friend's blood is worth bottling!

[Huzo]

Is it just me, or do Stelvios have a face like a slapped arse…

[dguzzi]

Agree!
  Also looks like you should not do burnouts or wheelies!!

[guzzdi]

No, the cover plate over square hole on LH side of front timing chest. Behind the LH upper frame mount.
2V models have a breather hose going there.

Hmm, I don't understand which plate at that location you mean (or my bike 4V doest have it?). I have there this hose you mentioned, if I understood the location you meant.

[guzzdi]

Good to see you got it all sussed Guzzdi.

Friend's blood is worth bottling!

Thanks, Muzz! And yes, I'm very grateful to the friend (and to you connecting me to )!

[guzzisteve]

Yes, 8V has a plate to take off to get motor out, behind 10mm allen goes into motor in front of cyl.

[Paul_Tim]

Yes, 8V has a plate to take off to get motor out, behind 10mm allen goes into motor in front of cyl.

Early models have a deep plate held by two bolts , one of which is impossible to access with the motor in the frame and which makes motor removal/installation a pita. I believe later models have either a much thinner plate or it's blanked off thus making motor movement a lot easier.

[GMies]

Tris,

I don’t have here in Seattle access to such level metallurgists :)
Besides that, I cannot even imagine what are possible any other reasons except manufacturing defect? I was single on a bike, going uphill gravel road, no luggage, on a second gear about 20 km/h.
Uphill steep, but I wouldn’t think of it as something extraordinary from a bike load perspective.
And what is a point to “prove” manufacturing defect? The bike is out of warranty anyhow…

Cheers

“Besides that, I cannot even imagine what are possible any other reasons except manufacturing defect?”
You are driving at too low an engine speed?

[guzzdi]

If you can get a couple of good pictures of both the fracture surfaces I can show them to one of our metallurgists
Can't do the lab work, but obvious stuff they'll spot and interpret from the pictures

Tris,

Not at home now.  I'll try to take the better quality close-up picture(s) of both parts (the shaft itself and small broken piece) sides in couple of days, when I'm back.
Meantime, attaching a couple I have on my phone now from small piece:
1) with a focus on a center of the broken small part
2) with a focus on an edge of the broken small part




:

[guzzdi]

“Besides that, I cannot even imagine what are possible any other reasons except manufacturing defect?”
You are driving at too low an engine speed?

I don't consider 20 mph on a second gear uphill as "too low an engine speed".. Especially on a bike like that, which was "derived' from Griso/Breva as an "adventure tourer and reportedly has been optimized for an improved torque curve.
And in any case, whatever engine speed and/or gear was (even if a hypothetical rider didn't choose correctly), the shaft not supposed to break like that...

[Alfetta]

The use of splines for an off-road machines is a bit troubling in my mind. 
If the splines are not "pressed" together then there is an amount of clearance that will allow torque reversals to occur when the tire suddenly gains or looses traction.  Over time the impacts imparted by the torque reversal will fatigue the metal, especially if the is any small imperfection present. (machining or base material)

I did see a small dark spot on the broken shaft end,  but I cant see I this is an inclusion of a spot of debris.
I could also see metal migration on the sides of several splines, and that would indicate to me that the clearances are even larger than the original slip fit values.

[tris]

From these shots it looks like the surfaces have spun on each other  - which is not a huge surprise I guess
Problem with that is that all the stuff that gets the metal men excited is  lost.
Still let's see what we can see once GD gets some nice photos square on

[pauldaytona]

I had the same a few years ago with a 2008 stelvio, could be my pictures. Mine broke when I was using no power, rolling down a trafic light. Bought a new shaft and build it in, did change the clutch to a new one to have a light clutch

[guzzdi]

I had the same a few years ago with a 2008 stelvio, could be my pictures. Mine broke when I was using no power, rolling down a trafic light. Bought a new shaft and build it in, did change the clutch to a new one to have a light clutch

At least now I know I'm not that special 
Since September when it happened, I posted here and couple of other places and everybody everywhere told that they not only never seen, but never heard of something like that.
To be fair, I also didn't see and didn't hear of similar, not only on Guzzi, but on any bike 
I also wanted to replace the shaft itself, but ordering a new one from europe was a wait of 2-3 months, as estimated by a couple of dealers I UK and Italy I requested a quote.
Also realized from the quotes that new shaft cost + shipping is the same (actually even little higher) than buying used gearbox I found.
Thanks for sharing your case.

[John A]

On the plus side , if you’re not breaking parts, you’re not putting out enough power….

[Wayne Orwig]

Early models have a deep plate held by two bolts , one of which is impossible to access with the motor in the frame and which makes motor removal/installation a pita. I believe later models have either a much thinner plate or it's blanked off thus making motor movement a lot easier.

My 2009 had that goofy breather plate. No way you could simply drop the motor from the frame. And no way to unscrew the plate with the frame in the way.
It took a lot of wiggling and cursing.

[ohiorider]

Pinwall has several Guzzi transmissions.

https://pinwallcycle.com/advanced_search_result.php?__Secure-osCsid=b256734d82a65e788b0756aca6e9b5f7&keywords=moto+guzzi+transmission