Drive Spline Failure

[SmithSwede]

Went to replace my rear tire.   Upon removal a bunch of little black plastic like balls fell out of the cush drive area.   Well that’s odd.

After mounting the tire I went to lube the final drive splines. Pulled the drive unit off the swing arm, and the whole thing is filled with orange and black dust that is only slightly sticky.  There was nothing resembling grease left on the splines.  They were dry, rusty, and severely worn.   Had to hammer the mushroom head coupler out of the flat sided coupler.  Unfortunately the splined end of the driveshaft/U-joint assembly is also chewed up and a very sloppy fit.  So basically these components are shot after 86,000 miles.

I’m pretty surprised by this.   I have regularly lubed these splines, every 10,000 mile or so, whenever I change the rear tire.   Always used GuardDog 525 moly spline grease, which the BMW guys all say is terrific stuff.   Until this time, the grease was always greasy, still on the splines, and the splines always looked absolutely brand new with no discernable wear.  Looked to me like they might last forever.

But this time the lube was either a rusty/crusty gritty type of dust, or it was so hardened and caked onto the splines that it was hard to scrape it off even with a sharp screwdriver. 

So what the heck happened?   Failure of the lube?  Or was something mechanically wrong and that caused the lube to turn to dust?  I’m pretty sure it’s not water contamination.  I’ve had water in the swing arm before I sealed the boot, and it never seemed to affect the grease.  No longer get water in there.   And yes, all the parts were present and in the right location, like that little spring on the end of the drive shaft. 

I would have expected the failure mode of these splines to be slow, gradual and even wear over an extended period of time.  Not going from looking brand to totally buggered in 10,000 miles. 

[delrod]

I have nothing. Except maybe you've been a bad boy and this is some sick Santa version of coal

[Mr Revhead]

What's the bike?
Is it possible the cush drive has gone hard and the shock loading did it?

[Muzz]

I use a moly grease Swede and it has never gone hard on me.  Smother it every tire change.

Revhead, I think he has a V7 smallblock.  If the cush blocks are anything  like the Breva they go soft instead of hard.

[oldbike54]

 Swede's bike is a 2013 V7 , hi-zoot moly grease . At 86K miles I would expect a problem or two .

 Dusty

[jacksonracingcomau]

it is the sb weak link apparently fixed v7/3 and v9
on my 8v sb I caught it just before fail but is obvious will happen again. lubing all we can do replace bits as worn, on mine driveshaft still good, fluke , another few miles it would of gone too or maybe ripped coupler first ?

hope they have it right now v85 cannot afford weak links. this was intended for v35/v50 maybe ok for them, def. oot up to any serious use
factory race ( dakar) sb’s used bb swinging arm and drive box they knew then
merry and happy etc

[Sasquatch Jim]

 It is a contagious disease, now that you have put those pictures on this site, we have all been
exposed to contamination.

[sign216]

Swede's bike is a 2013 V7 , hi-zoot moly grease . At 86K miles I would expect a problem or two .

 Dusty

86k miles is plenty, but I still feel like this spline wear is premature, especially since SmithSwede keeps up on his maintenance.

Perhaps a batch of splines that wasn't sufficiently hardened, or made too hard (so less tough).  Open to ideas. 

Joe

[wirespokes]

Do you clean the splines really well every 10K, and then apply new lube?

[SmithSwede]

Well, I would not say I cleaned the splines “really well” before re-greasing them.  I’d wipe off most of the old lube with a paper towel and then just slather on new grease.  I certainly did not use solvent or a toothbrush to clean everything back to bare metal. 

[RinkRat II]

    After looking at the uniformity of the failed parts, I would be inclined to think that they are probably case hardened and over time the hardened layer wore down to the softer base metal and then it wouldn't take long to destroy itself. (10,000Miles)  Possibly not hardened properly to begin with , I would think with the frequency you lubed them they should still look new or pretty darned close.  Really the only way to be sure is to send them to a materials testing lab, but that ain't cheap. My $.02

     Paul B

[timonbik]

Even if the splines were never lubed this type of failure is really quite unacceptable.   Think about car driveshaft splines that literally go 100,000's of miles without servicing.  Rarely ever do you hear about this type of failure in the automotive world.  We accept far to many substandard manufacturing practices from the motorcycle industry.   If Hyundai or Kia can build a relatively reliable car for $10,000 why can't M/C manufacturers build a motorcycle at the same price point with the same reliability.

[Zoom Zoom]

I'm kind of leaning in the same direction as Mr Revhead. Could some unwanted slop elsewhere in the drive line have caused excessive wear to the coupling?

John Henry

[SmithSwede]

I’m liking the theory that the case hardening wore through.  The wear is very uniform.  I don’t see a piece chipped off or some kind of obvious mechanical damage—just severe wear and rounding over. 

Shock loading? Well, the rubber bits in the cush drive and nice and rubbery.  And not to brag, but I’m very smooth in up shifting.   I don’t normally use the engine to decelerate, instead pull the clutch and use the brakes. 

Is there another source of shock loading?   Maybe something going bad in final drive? 

The clutch was replaced at 65,000, and most of the shock springs on the old clutch were broken because the housing had cracked.    On the other hand, the splines still looked new when I put in the clutch.

[sign216]

I must disagree.  The case hardening didn't wear through, because case hardening is not appropriate for this part, and Guzzi never would have used it.  They would have "through hardened" the part, but I'm guessing either the alloy or the process wasn't correct and the hardening wasn't properly done. 

[Chuck in Indiana]

Hmmm. Why is case hardening not appropriate? I would think a spline would be a good application for case hardening.

[voncrump]

I have had a couple of good looks at the photos.
The two worn splines have not been very deeply engaged.
From memory without the parts in my hand to work it out properly I think you need to check that you have assembled the parts in the right order.
From memory there is a spring that should hold that side of the coupling together.
If the circlip in the coupling is on the wrong side of the disc the spring won’t hold it together.
The parts drawings are not very clear how it fits together.
The whole coupler seems to be a bit of a wearing replacement part.
A weak link to protect the drive box?

[SmithSwede]

Yes.  The wear only extends half way down the coupling.  It was like it was frozen and could not freely move.

But I’m quite confident it was assembled correctly.   Maybe spring weakened?

[fotoguzzi]

Where is Pete Roper on this?

[voncrump]

In the top picture the circlip looks polished on the back side.
For it to be polished by contact with the rear part of the drive box coupler it would need to be engaged deeply as the spring would encourage it to do.
Just from memory the disc sits on the front side of the circlip.
If the disc  was fitted on the rear side of the circlip the spring would be ineffective in holding the coupler firmly engaged on the rear join.
The spring in the end of the driveshaft pushes on the disc, the disc pushes on the circlip and that holds the coupler back onto the part in the lower picture.
If the only wear you can see is between the rear of the coupler and the spline that slides onto the drive then just replace those bits.
I would say that the coupler has had a fair lifespan .
As long as the front end is good along with the driveshaft replace the  2 bits, slap it full of grease and ride.
Cheers, voncrump.





This diagram is not a good guide because it shows things in the wrong position.
I feel the circlip and the disc should be shown at the front of the coupler.

[Chuck in Indiana]

[This diagram is not a good guide because it shows things in the wrong position.quote]

Luigi was promoted to engineering for a while, but eventually demoted back to not greasing bearings on the production line. .

[SmithSwede]

Yes, I assemble it so the disc sits in front of the circlip—the disc is closer to the front wheel, and the circlip is behind it. So the spring bears on the disc, which cannot move past the circlip.  Thus the spring tends to push the rest of the assembly back towards the final drive.  If you did it the other way, the spring would be pushing the disc up and down the coupler on the back side of the circlip, which doesn’t seem logical. 

If that’s wrong somebody sing out. 

[guzzisteve]

Yes, I assemble it so the disc sits in front of the circlip—the disc is closer to the front wheel, and the circlip is behind it. So the spring bears on the disc, which cannot move past the circlip.  Thus the spring tends to push the rest of the assembly back towards the final drive.  If you did it the other way, the spring would be pushing the disc up and down the coupler on the back side of the circlip, which doesn’t seem logical. 

If that’s wrong somebody sing out. 

You have it right!! Parts wear out. There IS a reason it is changed on the V9, more poop=more wear.

In the top picture the circlip looks polished on the back side.
For it to be polished by contact with the rear part of the drive box coupler it would need to be engaged deeply as the spring would encourage it to do.
Just from memory the disc sits on the front side of the circlip.
If the disc  was fitted on the rear side of the circlip the spring would be ineffective in holding the coupler firmly engaged on the rear join.
The spring in the end of the driveshaft pushes on the disc, the disc pushes on the circlip and that holds the coupler back onto the part in the lower picture.
If the only wear you can see is between the rear of the coupler and the spline that slides onto the drive then just replace those bits.
I would say that the coupler has had a fair lifespan .
As long as the front end is good along with the driveshaft replace the  2 bits, slap it full of grease and ride.
Cheers, voncrump.





This diagram is not a good guide because it shows things in the wrong position.
I feel the circlip and the disc should be shown at the front of the coupler.

The diagram is the same in the service manual from 1981, Luigi has not changed his ways!!

[wirespokes]

The reason for totally cleaning the splines is to remove any grit developed since the last cleaning. The grease holds it in suspension, and turns into a grinding paste.  So yes, it's important to totally clean splines down to clean shiny metal and then add grease - with moly in this application.

[SmithSwede]

Thanks wirespokes, I had never considered that.   Since I never did clean it down to the bare metal as you recommend, I am now wondering if the actual spline contact areas were filled with old dried up grease and metal wear particles.   Which I simply covered over with a new slathering of grease.   So it looked well lubed, but maybe not so much in reality.   

Some of the grease that was actually in the splines was hard as a rock.  Hard enough that it was difficult to chip out with a sharp screwdriver.   

New parts en route.  I’ll clean them good in the future.   

[TimmyTheHog]

Trying not derail the thread :P

But if that spring (4), disk(3) and rear circlip (12) is at the wrong spot in respect to the cylindrical coupler (5) ,how would they go in together?





Like this or am I smoking something?

I didn't take Rear bevel off last time myself when having the rear tire change...so...ya... lol

[Antietam Classic Cycle]

In new color appropriate packaging. 

[geodoc]

My particular favorite:






.

[Antietam Classic Cycle]

My particular favorite:






.

Never had much luck with it. Pounds out, flings off, splines left dry as dust.

[guzzisteve]

Just got off the phone w/Karl W, his V7 II has over 100K mi on it and never any lube on splines, my Cal2 has 130K mi pulls a sidecar over 100k mi and no lube on splines.  I think it's all BS!!! No one here worked on farm machinery, if you lube stuff it collects dust and wears faster.