Clutch Spline Failure Analysis

[boxermania]

trout

Let me answer your questions.....as they are very valid.....

You offered a conclusion, but really no recommendation.

You are right, as I know what is the mechanism that leads up to the failure but not what started it in the first place as there are several bolted joints that can lead to the angular misalignment in question.....the easiest way to visualize the issue is if you look at a TV (top view) of the engine-tranny joint and consider that there is a vertical plane at the joints that will be mentioned below. This vertical plane has to be parallel to the next, within a small tolerance, that will not induce the premature wear of the mating components, i.e. the splines of the clutch disc and the splines of the tranny input shaft. I'll start from the engine and move back towards the tranny.....

1) The center line of the crank
1) At the mating of the engine case with the transmission case
2) At the mating between the crank flange and the flywheel
3) At the mating between the flywheel and the pressure plate
4) At the mating of the transmission case and the mating of the engine case (this is the opposite from #1, as the vertical plane of the tranny could also be the problem)
5) The center line of the input shaft

Note that the point of flexion is between the clutch and the input shaft spline, so if the angular misalignment is on the clutch end the "gap" will be on the right side of the engine, if on the tranny side the "gap" will be on the left side......have I thoroughly confused you by now?

Are these bikes considered (by you) to be non-trustworthy?

I had one and never was concerned about the problem, probably because if it happened to me I had CPO coverage and it would have been a challenge for me to get to the bottom of it. It does concern me that there have been sufficient number of failures to alert the OEM to a potential problem and they, for the most part, have ignored the issue. The failure will not cause you to wreck, thank God, if you are on a little traveled road but picture as to what could potentially be the outcome if you are on the slab at 80 mph in one of the middle or left lanes and all of a sudden you loose motive force.....would that be dangerous to your health?

I think I have answered all your questions......hopefully.......

[boxermania]

fnfalman

Sorry to hear about your experience....another data point, (03 Rockster at 26K miles). Did you have to shoulder the repair?

Please revisit the first post and see if your clutch disc looks similar to the pictures posted of tor1150r failed parts (he had his mishap at 39.9K and 66.7K and sold the bike afterward). If your clutch disc looked like the picture and the event took place 13K miles earlier, that in itself tells me that your bike has a greater degree of misalignment than tor's. If your bike was repaired, but the problem was not solved, I suggest you get the splines inspected at around 40 K miles to be safe, if you choose not to do it, I would stay close to home as the odometer approaches 44K miles......

Best of luck to you.......

[fnfalman]

My male end wasn't too bad but the female end was completely stripped. Like I said, had I known about this thread I would have taken pictures for posterity. My failure isn't anywhere as bad as Tor's though. Not only that but I found a junker Rockster at a local salvage yard and got the whole tranny and did a straight swap because I didn't trust the rest of the tranny either. My guru recommended that course of action instead of just replacing the parts and I got the tranny for like $150 from the junker Rockster.

[Trout]

Let me answer your questions...I'll start from the engine and move back towards the tranny.....

1) The center line of the crank
1) At the mating of the engine case with the transmission case
2) At the mating between the crank flange and the flywheel
3) At the mating between the flywheel and the pressure plate
4) At the mating of the transmission case and the mating of the engine case (this is the opposite from #1, as the vertical plane of the tranny could also be the problem)
5) The center line of the input shaft

...I think I have answered all your questions......hopefully.

Thanks again for the great info. I have one more question. If the misalignment is caused by poorly built parts or machine work that is out of tolerance, then is it true to say that the misalignment cannot occur from R&R of the transmission? In other words, if I pull the transmission to inspect the parts, and if the parts look perfect, then could I cause a misalignment when I bolt it back together?

[awagnon]

Boxermania, thanks for the work and the post. I've been following spline failure threads on this forum as well as the AdvRider, BMWMOA, and BMW Sport Touring forums. As you know, there was a spline failure survey on the BMWST forum about a year ago which showed an increased spline failure rate with 2002 RT's. But, as you said, they may have simply had more miles on them. My splines failed on my '02 RT at 43,000 miles. They looked like the ones you photographed, except worse.

I agree it's a shame that BMW won't come out with a comment or statement concerning this issue. I'm sure they have data on the incidence from their warranty records. If the incidence is low and acceptable, then they should say so. I suspect it isn't, so they're quiet. As I mentioned on a BMWMOA forum thread, I wish the MOA would actually represent BMW riders and challenge BMWNA to address the issue. If not, the MOA could at least sponsor a survey to try to find out the incidence of this failure. Other brands of bikes have had similar expensive design issues and declined to address them until owners' groups forced the issue. I don't expect BMW to act any differently.

It would be unrealistic for BMW to admit a design flaw and order a recall for inspection and repair. However, they could extend the warranty on just the splines and go a long way towards earning respect.

[OU812]

That's it. A Suzuki Kawi Hondu ZX145475432 for me next. Or what ever won't keep me awake at night.
Really great thread Boxer maniac!
Really.

[boxermania]

fnfalman

Well you were very lucky to come out as well as you did and being able to latch on to a tranny. Do you still have the old tranny?, if so maybe we can put to rest some of the unknowns.Before proceeding on my end I would have to ask you one question.....and don't feel bad if the answer is NO as I have to ascertain if you can perform the task......If I ask you to sweep the the tranny housing with an indicator mounted on the input shaft would you know what to do?

Bless you if you do, because we can find out if the problems lies in the tranny.......even if you don't have the tools I'll rig something up and send it to you. The oter thing to do, is to grab the input shaft and see how much free play, side to side, up and down, there is......I wouldn't expect to see much.

Just thought of a question, did you notice alignment pins at the mating surfaces between the engine and the tranny.....if so:

Where are the pins located and how many, I woul have to guess on the engine side. Can you send me or post a pic of the tranny front, as if you were facing the input shaft.....one of the damage on the input shaft will help as well, only if you feel like it.....thanks.

[boxermania]

Trout

There are two types of misalignment, parallel and angular.

Parallel occurs when two items that are to be on a center line are displaced side to side…..in our case that would play out if the engine was laterally offset to the tranny. (side to side, north to south)

Angular would be when the engine and tranny don’t square-up, in other words one side of the mating faces touches earlier than the other and it could be anywhere on the contact surfaces. This will in essence put a “kink” on the required center line.

The spline wear exhibited in these failures is heavy on one part of the spline, not the whole spline, which is typical of angular misalignment. Parallel misalignment is a bit more complicated due to the design of our bikes and I’m not going to go there at this time, but the result would be manifested eventually, as the same heavy spline wear but along the majority of the spline length.

Likewise the engine and tranny mating faces have guide pins that if in place and placed in the proper position, insure that the centerline between the crank and the tranny input shaft is maintained. This prevents parallel misalignment.

In answer to your question, NO, the spline problem can’t be brought about by R&R of the tranny.

Now my question, are you planning to inspect? Inquiring minds want to know!!.....

[Trout]

Now my question, are you planning to inspect? Inquiring minds want to know!!.....

Yes. But probably not until the end of the riding season. I need a bike that I can take to Alaska next year and not be worried about a catastrophic failure in the Yukon territory. My 2002 R has about 15K on the clock and should have 20+ by the end of the summer. I'll pull the tranny off this fall and see what the splines look like. If the splines look perfect, then I'll bolt her back together and not worry about it. If the splines show any abnormal wear, then I'll sell the bike next spring and be done with boxers (or BMW's for that matter).

[boxermania]

Trout

Understand your position perfectly.....NOPE, you definitely don't want to have a failure of this kind while visiting Alaska as it would make you a very unhappy camper.

If the splines look perfect, then I'll bolt her back together

I think the statement above should be......If the splines do not show abnormal wear......

Best of luck to you.....please keep us posted as I hope to get to the bottom of this........

[boxermania]

Just to provide a visual representation of the diferent cases of misalignment. Look at the drawing from a bird's eye view perspective.........angular misalignment is what I believe is taking place, however, note that the way it was drawn, the tranny is out of alignment to the engine, when, it could very well be the other way, namely, the engine being out of alignment to the tranny.



As a matter of fact since there are more vertical planes on the engine side the probability is higher that the problem is sourced on the engine side.

Ps. Left a couple of things open for comment for those that enjoy root cause FI.

[awagnon]

Boxermania, of your five possible causes of misalignment, I've seen documentation of axial misalignment which was corrected by relocating the alignment pins or a new transmission. Yet, there is still no proof this will prevent repeated failure or if the misalignment actually caused the failure. Seems like speculation. According to the analysis in the BMWRA magazine, the problem is due primarily to the input shaft not extending all the way into the clutch splines. There is an after-market input shaft that is 6 mm longer and extends to flush on the back side of the clutch spline and made with harder steel with less spline lash. Again, who knows if that will correct the problem.

When I looked at mine, I thought it looked like an angular misalignment due to the wear pattern. To me, the mounting contact area between the flywheel and engine crankshaft flange seems awfully small. A tiny error on one side would result in a significant angular misalignment. If a tiny fleck of metal or rough edge was under one side when the flywheel was bolted on, then you would get an angular misalignment. I started to remove the flywheel and re-bolt it, but was warned not to because the bolts have shallow heads and are quirky. Also, who knows if it wouldn't have made matters worse.

I suspect the cause is multifactorial with some failures due to different causes. However, I suspect the majority are due to a single design flaw and BMW knows the reason.

-Al

[boxermania]

awagnon,

I have also read with great interest what has been written regarding axial or parallel misalignment. The wear on the input splines supports angular misalignment, however, after your post I sat down and visualized another potential scenario.

We know, for a fact, that the clutch splines don't engage the input shaft splines fully. Since the clutch disc is in essence overhung buy about ~ 20% of it's active lentgh, there is the potential the due to the design clearance between the splines, as the rotational force of the engine on the clutch disc loads the splines, the disc "rocks" or "dingle" on the input shaft splines. Now, if on top of that we factor a bit of axial/parallel missalignment, I can understand the type wear that can resemble what has been experienced....

Once again and IMO, this goes back to the fact that in the BMW design the crankshaft and the tranny input shaft are allowed "to float" linearly relative to each other, unlike automotive applications where the tranny input shaft stabs onto the rear of the crank via a bushing or a needle bearing to insure the centerline between the two remains true.

Your mention of a 6mm longer input shaft, which BTW is the first time I hear of it, does come close to my measurement of .137" or 3.5 mm of unused spline. Hmmmm....another interesting development, thanks for bringing it to my attention.

[awagnon]

The aftermarket input shaft is made, I believe, in Canada and costs $900. However, if it really works, it would be worth the $$. I have a flyer somewhere I can post if anyone is interested. As I said, it is supposed to be machined out of harder stock with less spline lash.

[boxermania]

awagnon,

Please see if you can find the flyer, as the longer shaft, albeit a bit costly, certainly corrects one of the OEM's design flaws. Likewise, it would be advantageous, to those that might fall prey of this failure, to know about it.

Great work.....we are moving in the right direction, thanks once again for you input....

[awagnon]

Likewise, it would be advantageous, to those that might fall prey of this failure, to know about it.

Here is the link to the flyer: http://www.sunshinecoast.ca/bmw/InputShaft.pdf

I have no personal experience with it, but someone may find it useful. I replaced my input shaft with an OEM shaft. Now I wish I hadn't.

-Al

[fnfalman]

fnfalman

Well you were very lucky to come out as well as you did and being able to latch on to a tranny. Do you still have the old tranny?, if so maybe we can put to rest some of the unknowns.Before proceeding on my end I would have to ask you one question.....and don't feel bad if the answer is NO as I have to ascertain if you can perform the task......If I ask you to sweep the the tranny housing with an indicator mounted on the input shaft would you know what to do?

Bless you if you do, because we can find out if the problems lies in the tranny.......even if you don't have the tools I'll rig something up and send it to you. The oter thing to do, is to grab the input shaft and see how much free play, side to side, up and down, there is......I wouldn't expect to see much.

Just thought of a question, did you notice alignment pins at the mating surfaces between the engine and the tranny.....if so:

Where are the pins located and how many, I woul have to guess on the engine side. Can you send me or post a pic of the tranny front, as if you were facing the input shaft.....one of the damage on the input shaft will help as well, only if you feel like it.....thanks.

I feel worthless. I don't have the old tranny any more. It was traded back in to the salvage yard and I went back to see if I can locate it and take some pics but it was thrown away!!! The owner of the salvage yard (LA Salvage) wasn't onsite that day and the guy that sold me the tranny and took in the trade, upon hearing that my tranny was blown, decided to chuck it instead of "salvaging" it for other parts.

I don't remember seeing anything out of place other than the male and female were screwed with the female end being the worse of it. My guru was pointing it out to me while explaining that the rest of the parts (flyweight, clutch plate, et al) seemed fine, but he figured that since we could get a whole new unit, just take it instead of swapping out the splines.

[boxermania]

I thought I would revive the thread as it appears that the spline failure has resurfaced again. Lobo1625 apparently has access to machine shop equipment and is considering improving the breed, eventually, the little people will conquer the ill........

[Daryl_stamp]

Der Furer verstanden vas ist schlect mit der BMW motorrad;
http://youtube.com/watch?v=ukAhlxl4hmM

I'm @ the 24K service interval on an '02 RR.
I ride it like I stole it.
I'm a little concerned about an impending failure, especially far from home.
but it's not an adventure until something goes wrong anyway, and who isn't up for a little adventure.

FWIW, I have a rudimentary machine shop in my basement and would be willing to help anyone, although I don't call myself a machinist.

As far as splines go, the electric motors (o.5 to 7.5 HP) that we manufacture at my company use a spline to fit to the driven device.
I spoke to my colleague regarding the normal processes used for splined shaft manufacture;
- forming (similar to thread forming, only spline forming, or really deep knurling)
- broaching (similar to a really long file w/ proggressively deeper teeth, as the broach feeds more material is removed)
- rotary tool cutting & indexing (similar to gear cutting, the rotating cutting tool matches 1 'tooth' of the spline, the shaft is rotated between cuts)
- powdered metal forming (literally powdered metal, pressed to shape & baked); the part that mates to our motors uses this technology; this is generally not used for complete shafts, only adapters.

The process selected depends on the quantity required & the degree of accuracy desired. Knowing what process BMW uses would aid in identifying root cause.
There has to be someone on the board that has some automotive background that could shed light on the likely process @ Gertrag or who-ever it is that makes them.
As far as a $900 aftermarket goes, I can understand the price if they provide some guarantee (which means they've tested it enough to be confident in it's longevity).
The heat treating & subsequent finishing is probably more sophisticated than the garden variety rose-bud & bucket of used motor oil.

Regards,

DLS

[awagnon]

I noted an interesting development on the spline failure issue. A 2002 R1150R owner on the MOA Oilhead forum had his splines fail at 55,000 miles. When BMWNA wouldn't help with the repair, he filed suit in small claims court. His intent is mainly to find out the scope of the problem through the discovery process. I wish him luck. Perhaps if enough owners sued BMW or there was a class action suit, them BMW would extend the warranty on the driveline.