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I tried using the search engine on this site to find the stats on LT bikes that have had a final drive failure. No luck. Is it certain years, mileage, frequency of changing the oil, type of oil, loads carried or any of these. I've heard there was a correlation with the final drive bearing having either 17 or 19 balls in the race, with the 19 ball bearings being more prone to failure due to the smaller size of the balls.

I suspect this is an old subject. If this has been discussed in detail before please direct me to the thread.

My thinking is check the play, drop the oil, check the plug, fill it and go ride. Call Ryder as necessary.

Thanks :cool:
 

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This subject is an on going hot topic. Luckily we have our final drive guru, CharleyVT. check out his posts, he has really done some indepth studies of failed final drives. Most popular opinion on failure is improper preload shimming by the factory. This is why some LT's go forever without failure and others do not. Bad factory setup.
 

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While some of us have had the oil wet rear wheel and sinking feeling of a bearing failure only to find bearing was just fine having instead just a seal failure ... go figure :(
 

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I will decline the appellation of "guru", but I have been following reports of final drive failures for years now and have rebuilt about 30 of them. There are others who understand these things much better than I do, but are unwilling to share their knowledge or waste their time (bmw folks themselves, professional mechanics or engineers.)

Failure modes: The most common catastrophic failure is of the crown wheel bearing (this is the bearing that is commonly a 19 ball German bearing, but for a period on time BMW supplied a 17 ball French made bearing). I'll discuss my theories as to why these bearings have failed further below in this post.

There are two other less common causes of catastrophic failure that I am aware of: these involve the tapered roller bearing located at the opposite end of the crown gear assembly from the crown wheel bearing. In the case of primarily 2005 models, there is a lack of an interference fit of the tapered roller bearing on its shaft on the crown gear assembly. This has resulted in the tapered roller bearing spinning on its shaft leading to eventual failure.

Another mode of failure I have seen a couple of times is more unusual: in these cases the inner race of the input pinion shaft needle roller bearing slips down its seat on the pinion shaft and wears through the bottom of its recess in the final drive housing to the point where it can damage the tapered roller bearing. In the case of one final drive shipped to me, the inner race of the pinion shaft needle bearing had slipped of its seat and worn through the housing far enough to dislodge the speedometer sensor sending ring. The only symptom at that point was that the speedometer wasn't working; if this were to happen on a later year bike without the speedometer sending ring, the first symptom probably would have been catastrophic failure of the tapered roller bearing because that would have been the next thing damaged by the dislodged needle bearing race. This type of unusual failure has been photographed and reported on this board.

Addendum added by edit: Another mode of failure that I have seen first hand, and have read additional reports of is a failure of the press fit between the carbon steel and aluminum components of the crown gear assembly. This part is factory assembled and only available as part of a crown gear/pinion shaft set. In this failure, the interference fit between the carbon steel crown gear and the aluminum component is inadequate and slippage occurs between these two components. This failure was written up in a past issue of BMWON and was also seen by a member of this board who had FD lube come out the rear wheel bolt holes during a tire change. (another example of machining errors resulting in improper fitment between components).

Other final drive "failures" include leaking seals at both the rear wheel hub and the input pinion shaft. Any seal can leak without associated failure of mechanical parts and there have undoubtedly been a few of these.

I believe there have been reports of failure of the input pinion shaft assembly but these are very rare compared to the "classic" crown wheel bearing failure.

The "classic" crown wheel bearing failure:

Two oft repeated questions relating to the most common failure, that of the crown wheel bearing, are: 1) What is/are the cause(s), (the implication being is there something that can be done to prevent it?), and 2) Are there any signs of impending failure that would provide early warning that might help avoid a breakdown on the road?

1) Causes: Having rebuilt a number of drives with failed crown wheel bearings and having used two separate methods to measure for bearing preload as specified in the BMW service manual, I have consistently found that drives were delivered with excess preload. Consequently, I suspect that excess axial forces on the crown bearing result in eventual damage to the balls and races leading to bearing failure. Another possible cause might be that improper forces were used during bearing installation damaging the bearing. I do not believe that there is any evidence of superiority of the 19 ball bearing over the 17 ball bearing or vice versa.

IMO the root causes of all these failures is a lack of quality assurance in either the machining of FD components or in the assembly procedures.

2) Predicting failure: The evidence is pretty good that early warning signs are hard to come by. The reports of failure seem to suggest that the amount of time or number of miles between finding significant metal in the FD lube, or first feeling roughness in rotation of the rear wheel and ultimate seal failure and oil loss is small.

Some folks have proposed chip detectors as found on some aircraft but I haven't heard on anyone actually fabricating one (and I doubt it would provide much benefit); others have speculated that monitoring FD temperature might provide early warning, and someone on this board posted about actually fabricating one. I haven't read any posts about that effort, but I doubt monitoring temp would do much to predict a failure.

Two indicators that the FD crown wheel bearing is going bad are shiney metal flakes in the oil and roughness felt during wheel rotation. The “shake the wheel test” is often suggested as a test of final drive problems but I don’t believe it has any value in assessing the final drive; it will reveal loose pivot bearings or other swing arm problems. By the time looseness is felt at the rear wheel secondary to crown wheel bearing failure, there is probably already seal failure and loss of lube. One test I do put some stock in is feeling for roughness during wheel rotation; to do this I suggest pushing the brake pads back so they are not touching the rotor, or simply removing them, and then slowly rotating the rear wheel while feeling for roughness. Someone also suggested listening to the FD with a mechanic’s stethoscope while rotating the rear wheel, but I suspect feeling for roughness would be a better indicator. But again, by the time you can feel roughness during wheel rotation, by all accounts there are few few miles left before catastrophic bearing failure.

While really meaningful statistics are lacking, it seems that the earlier models 99-03 may have had the higher failure rates, but there have been reports of FD failure as late as the 2009 model.

Unfortunately, I have concluded that the only preventive measure beyond following the manufacturer's recommended lubrication intervals is preemptive rebuild of the final drive. Preemptive rebuild should include careful measurement of preload rather the just swapping out the bearing. The evidence is pretty good that rebuilding a failed drive by just replacing the bearing sets the stage for a repeat failure. More than one rider has reported multiple FD failures following BMW service department repair; I have to wonder how those rebuilds were done.

Summary conclusions: There are no “early” indications of crown wheel bearing failure. Roughness felt during wheel rotation or shiny metal flakes in the lube indicate that bearing failure has started, and few miles are left before the bearing retainer breaks and seal integrity is lost.
 

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I should have given credit in my post above to those gentlemen who have contributed to what I think we understand about the K1200LT final drives and how they fail. The original post by Dman who gave us the dial indicator method off measuring for preload, and the many posts by several mechanical engineers on this site who have offered observations, experiences, and insight relating to how the final drive is constructed and factors that might be contributing to failure.
All I think I know is based on my observations and their knowledgeable input. This has been a team effort and credit goes to all who have contributed.
 

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CharlieVT said:
I will decline the appellation of "guru", but I have been following reports of final drive failures for years now and have rebuilt about 30 of them. There are others who understand these things much better than I do, but are unwilling to share their knowledge or waste their time (bmw folks themselves, professional mechanics or engineers.)
Charlie does an in-depth explanation, succinct and to the point and he declines the "GURU" label??? There are those that walk the walk and there are those that talk the talk... Charlie does them both... and rather eloquently if I do say so myself...

Nicely done sir! And a huge THANK-YOU to all those who helped contribute... and continue to provide valuable info...

I am but a minion...

:bowdown: :bowdown: :bowdown: :bowdown: :bowdown: :bowdown: :bowdown: :bowdown: :bowdown:
 

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Final drives never fail! :eek: That is a myth started by jealous Wing riders! :alien::abduct:
Just ask BMW and they will tell you the same thing...!:rolleyes:
 

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CharlieVT said:
Some folks have proposed chip detectors as found on some aircraft but I haven't heard on anyone actually fabricating one (and I doubt it would provide much benefit); others have speculated that monitoring FD temperature might provide early warning, and someone on this board posted about actually fabricating one. I haven't read any posts about that effort, but I doubt monitoring temp would do much to predict a failure.
Any news on either of these systems being designed/made by now?
 

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earthman said:
Any news on either of these systems being designed/made by now?
I haven't heard of any, probably with good reason. Even if such proposed detection devices were to work, the amout of advance notice is very limited.
Read past posts regarding that document the rapidity of bearing degradation.
For the trouble and expense of installing an "early detection device" you can do a preemptive rebuild on your FD.
 

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While I am NOT here to debate Charlie's "GURU" status ... because he certainly is worthy of the title ... I would like to throw in my two cents.

My '06 GT's drive failed in Nevada. The cause was very clear to me, and I have yet to read this mentioned in this thread.

My final drive failed due to my incessant need to ride my bike. Had I just left her parked, it would have never failed.

Hope this helps. You've been warned. :)
 

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Great to read an "old timer" and contributor to this site "Messenger13"!

""For the trouble and expense of installing an "early detection device" you can do a preemptive rebuild on your FD."" CharlieVT.

I think there are others who have FD warning devices but mine may be the only one that uses the existing FD sump and a "chip detector". In tests it "warns" (speaker) and has a "red" warning light. It digitally resets and rearms it self and can be tested via a button push even when underway. It is a true Final Drive Warning System. I posted it on here some years ago and it has been working on my 99 K12LT ever since.

It is true what has been said about the short time that it takes for the crown bearing to begin to disintegrate. Subjective operator induced radial/axial wheel shake (bike on center stand) or FD fluid changes are hard pressed to detect incipient failure. But, early detection is important. It can save your FD from trashing itself where a simple crown bearing renew with proper axial "preload" can then be done.
 

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Well summarised (again) Curtis, great job. As I have suggested recently, and as you also state, what we have with the crown wheel ball bearing problem is known in industry as "short lead time to failure" and typically the only way to manage this type of issue on machines is by on-line vibration monitoring whereby known levels are set at alarm and shutdown points in order to prevent catastrophic failures.
In our case though, I still intend to connect our vibration analyser to the FD and try to get some meaningful data, but as with all VA exercises we need historical data for comparison, and ideally we also need to see a vibration spectrum from a FD unit with a known "over-preloaded" bearing. My '05 has 27,000 Km's and no fuzz on the mag plug (yet), but like you, I feel this really doesn't tell me much as I may not yet be into the beginning of the pF curve (failure potential), and if/when I do get to that point no-one really knows how short the lead time to failure is. So to shorten this already long story, I guess my 12,000-odd kilometre trip across the continent and return in September may add something more to my story, we'll see.
 

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Hi Dennis,

Thanks for you post. I always enjoy reading your input.

So you are going to ride 12,000 kilometers across the continent? You going to be running some kind of VA during the ride?

Have a great trip. :thumb:

For those who are experimenting with early detection with chip or heat sensors, I offer every encouragement. Nothing wrong with seeking earliest possible indication of a bearing failure. It is just that based on all I think I know of how these FD fail, if someone is on a long distance trip, a chip detector isn't going to make much difference. It might give you some extra miles of warning before the ride starts to feel rough but how many miles is unknown. That's why I say to those who are looking for "road insurance" a chip detector is going to be of limited benefit. I maintain that the best FD road insurance is a rebuild of the drive with replacement of the crownwheel bearing with proper setup, inspection of the tapered roller bearing and the input pinion needle bearing race. I think it makes sense to do that before investing in a chip detector. (I hesitate to repeat this because it will be construed as a solicitation by me to rebuild drives, which simply isn't the case.)




K100Dennis said:
Well summarised (again) Curtis, great job. As I have suggested recently, and as you also state, what we have with the crown wheel ball bearing problem is known in industry as "short lead time to failure" and typically the only way to manage this type of issue on machines is by on-line vibration monitoring whereby known levels are set at alarm and shutdown points in order to prevent catastrophic failures.
In our case though, I still intend to connect our vibration analyser to the FD and try to get some meaningful data, but as with all VA exercises we need historical data for comparison, and ideally we also need to see a vibration spectrum from a FD unit with a known "over-preloaded" bearing. My '05 has 27,000 Km's and no fuzz on the mag plug (yet), but like you, I feel this really doesn't tell me much as I may not yet be into the beginning of the pF curve (failure potential), and if/when I do get to that point no-one really knows how short the lead time to failure is. So to shorten this already long story, I guess my 12,000-odd kilometre trip across the continent and return in September may add something more to my story, we'll see.
 

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No Curtis, not during the trip, not possible with the gear we use. I'm going to try to get some meaningful data off the drive with it running at a constant speed. I think it will be possible, but I'll need to set the rear wheel on some rollers to simultate load in the correct orientation (pressing down on the wheel rather than suspending the wheel on the centre stand, though we may also do that as well, just to see what differences are seen, if any).
As for the trip, and risk associated with FD failure - the bike will be loaded to the full 600 Kg gross limit, and we'll be doing around 700 to 800 Km's dailly for the trip across the Nullarbor to Western Australia and same on return, the rest of the time will be tourist type mileage etc. Away in total for 4 weeks. If I have a problem it'll be the roadside assist number from the cell phone, then borrow my brother-in-law's R1200GS I guess, but I'm not counting on that as an issue. Ride it and enjoy I say. I reckon my '05 is a 96%er.
 

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Do the newer units, for the RT, such as since 08 or so still use the preload? I had been led to believe that the preload was no longer done on the newest final drives.
Am I wrong?
dc
 

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My opinion - Most of the heat generated in a FD is due to the oil being churned by the gearset. Very little will be from bearing load, and even less will be from a failed bearing. The nature of the metal on the magnet is the best first indication.
MN MechEngr
 

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David13 said:
Do the newer units, for the RT, such as since 08 or so still use the preload? I had been led to believe that the preload was no longer done on the newest final drives.
Am I wrong?
dc
You're correct, they use a needle bearing where they used to use a tapered bearing..
The main bearing is shimmed to set the backlash, no preload.
This style from 05 on the RT, IIRC, which has also been known to fail. This bearing is not lubed by the FD oil, sealed bearing. Can't use the over shim reasoning on this one. The P/N has changed for the replacement bearing.
Seems more to do with their design of a single sided FD then shimming but enough about FD's
 
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