Drive shaft failure

[Lucky Phil]

Thanks, guys!

 

Riding today, I recall another clue something had gone awry and I did not act on.  The week before the failure, the Sport started exhibiting an odd noise rolling up to a stop. It was a sporadic and not repeatable, "rowl-rowl-rowl" . . .  sometimes just one "rowl" or two. Reminded of the noise we sometimes get from the rear rolling the V11 backwards.

 

Evidently, that is pidgin Italian for, "Check your driveshaft."

Yes docc add it to the faint clunking/rattle feel through the footpeg on floating throttle when your rear wheel bearing is totally shot with about 500klms left in it.

 

Ciao

[danl]

Wow, that's a scary failure.  I'd sure like to not experience that one!  Glad it seems to have gone pretty uneventfully for what it was.  I have needed to re torque my u joint couplings a couple of times in the past (and I only have a third of the miles that Docc does).  I'm not sure how I noticed it the first time, but now I use a small prybar to try to slide the couplings fore and aft whenever I'm doing any work around the rear wheel.

 

I'm busy getting my newly resurrected V11 ready for the SSR, so last night I pulled the rear coupling off of the final drive to look for cracks.  It looks like Doccs cracks may have started at the root of the splines.  I'm surprised to see how dark one entire half of his coupling was.  It seems like it was running for a while with one side fractured all the way through.

[footgoose]

docc, you had asked me about a needle tip for greasing the front u-joint recently. I recall posting a photo... but I've lost it ... and the tip, so I got another today. Not the same but it works! Thought I should post results, a good a place as any. The sharp point is tapered and is just the correct size to depress the tiny ball in the zerk. It doesn't have a straight approach, but good enough to get the job done. Keeping max downward pressure, only a tiny bit gets out around the tip. The rest gets through to fill the little bastard.

O'Reilley's Auto Parts $15

[docc]

Those are kewl! Never seen anything like that.

Pretty sure my failure was a combination of my failing to torque pinch bolts correctly (go back and forth between them and not just once per side), not torquing to the higher side of the range (instead of the middle), and reusing fasteners that had been crossed and the threads chased. Is it possible that excessive pinion play may have contributed to rattling them loose?

Testing in process, as I have moved the back of the shaft to another reardrive almost 400 miles ago. I must have clicked the torque wrench back and forth between those bolts twenty times!

(Trying to earn my back . . . )

[Andyozz]

Guys.
I've read this post with interest and decided to check the UJ's on my newly purchased 1996 1100 sport.
No play in joints but both clamp bolts are torqued up correctly ( backed them off and 're torqued) and the UJ still slides on the splines.
Is this normal or have I got a more sinister problem On my hands?

Regards
Andy

[stewgnu]

Isn’t there a groove there that means there’ll always be a bit of fore-aft wiggle?

[docc]

When I first retourqued to the front yoke to the slightly higher value, it clamped tight to the output shaft.  After a couple thousand miles, the sliding play returned. I was tempted to retorque it again, but the fasteners have not loosened.  So, good question. Is the sliding movement normal and acceptable?

[luhbo]

I'd say this is not acceptable, even when it's quite common. Make sure you use 12.9 bolts and torque them to 40Nm. You may also cut the slots some millimeters deeper to ease the clamping. Of course, that's up to what nerves you have in real life, internet off. But done properly it's a proofen modification.

Some words about the alignment: Because of the wide rear tyre the U-Joints don't move in one plane only. Look from above and you'll see the shaft pointing outwards. That's the reason they weld them with some degrees more/less then 180°, it's to reduce the resulting transmission failure.

And be easy with grease on the moving part of the shaft. The spines should be able to glide 'freely', too much grease and they're stuck. Common fault because this zerk is the only one everyone can reach

[Pressureangle]

I found the bolts on my '97 to be f***ing TIGHT. But both ends still slid on the shafts. After <insert u-joint horror story> I cleaned everything and tightened the bolts until I felt the yoke clamp  the shafts, then torqued. In the end it was to about book spec for that fastener/thread, which escapes me at the moment. My conclusion is that the fit and finish at the factory, coupled with inadequate initial torque allows a bit of wear- or 'smoothing' and goes slack in the splines. Has anyone read the factory maintenance documents, to find if they recommend periodic retorquing?

[docc]

Preparing to ride the Fifteenth South'n Spine Raid,  I am reviewing all of my maintenance, failures, and repairs over the last two and half years.

My Sport's "100,000 mile service" (which has spanned just over 12,000  miles ).

After poring through this entire thread, again, looking for clues and issues, something poignant occurred to me that could shed light on the apparent "old" break in the driveshaft yoke.  The bike crashed at about 30,000 miles sliding on it's right side impacting the rear tire against an oncoming BMW sedan. Although relatively low speed (hey, people break bones walking into furniture! ),  the rear wheel was gouged, swingarm bent, and gearbox cracked.

It occurs to me that may have influenced the fate of the rear yoke. No way to be sure now, but the shaft is definitely in that "kinetic chain." Perhaps it was stable enough until the yoke was removed and retorqued twice in 2,000 miles dealing with the reardrive swaps. The crossed fasteners and re-cut threads remain on the list of "bad practices." As I say, no way to know, but the impact seems a significant concern, in retrospect.

[gstallons]

HMMMMM.  look at it and think , if the u-joint cap failure allowed the cross to twist the yoke and cause it to break ?

[docc]

I don’t think the cap failure came first, but IDK. I was thinking pure fastener failure, but now consider the impact may have predisposed that. No doubt, crossing the pinch bolt threads is both common and potentially disastrous.

While I could, once again, be accused of overthinking this, the failure was serious enough to warrant careful review and consideration. If my posts help one other rider avoid a come-apart, then we have success.

[docc]

2 hours ago, Mikko said:

So the driveshaft is a two piece design? 

Well, yes, the longer front section and the shorter rear slide together.

Each shaft section also includes a U-joint (cross) and a yoke that pinches onto the shafts. Three Zerks ( each cross and the slide coupling.)

[gstallons]

Uh , the arc of the swingarm is the reason for a two piece driveshaft . When the output shaft , swingarm pivot and the rear axle centerline are parallel , the distance is the greatest .

[Lucky Phil]

4 hours ago, Mikko said:

Ahhh okay... I understand it now. I wasn’t thinking of arc... thanks for clearing that up and I guess I’ll scrap that idea. 
 

I’ve been busy trying to figure out how to slim down and remove as much weight from the rear drive area. I had thoughts of a 1pc carbon shaft... but it looks like that’s a no go.

Next idea is to have measurements made of the rear drive to see about casting it in mag. The rear sub frame, swing arm and pork chops are already in the works.

I’m very confident of not only reaching my goal of 100lb off the bike, but exceeding it. Thanks for the help.

If you want to really improve the bike and save a massive amount of weight and dont mind spending money commission an elegant chain drive conversion and rid the bike of the heavy leaky inefficient POS shaft drive system altogether.

Ciao