BMW Luxury Touring Community banner

1 - 20 of 239 Posts

·
Registered
Joined
·
4,404 Posts
Discussion Starter #1 (Edited)
Much discussion and speculation about what indicators might be useful for predicting final drive failure.

I continue to try and understand the progression of the "classic" crownwheel bearing failure in our beloved K1200LT. I have now done about 50 final drive rebuilds, both repairs of various types of failures, (the most common being the "classic" crownwheel bearing failure) and a number of preemptive rebuilds. In several of the "preemptive" rebuilds the owner had become suspicious of dark gear lube, increasing grey metal fuzz on the drain plug magnet, and in more advanced cases, weeping of lube at the hub seal.

I have noted in past preemptive rebuilds that in many cases the outer race of the crownwheel bearing is wallowed out. More recently I have seen cases of where the hub seal had started to leak without other signs of catastrophic failure. In these cases, the crownwheel bearing outer race was severely wallowed to the point where one side of the groove had developed a very sharp edge. In the attached picture, I am trying to demonstrate how sharp the edge of the groove gets by shaving a finger nail on the edge of the groove. In this particular race there is also significant pitting, but in some cases the groove is smooth with out any pitting, but the groove is widened and very sharp on one side.

The only other signs of a possible problem other than weeping at the hub seal was dark gear lube and lots of fine fuzzy metal on the drain plug magnet.

Previously, I had maintained that grey fuzz on the drain plug was "normal" and shiney metal flakes were bad. Now it seems that grey fuzz maybe normal but may also be associated with wearing of the race without pitting. Metal flakes are definitely associated with pitting of the races.

In no case that I am aware of a "wiggle test" or "shake the wheel test" indicating a failing final drive. My suggestion is that if you are trying to find an indication of final drive failure, checking the rear wheel for wiggle is a waste of time. Even when the races of the crownwheel bearing was wallowed out enough to cause weeping of oil at the hub seal, there have been no reports of detectable wiggle at the wheel; the looseness is apparently too subtle for the human hand to detect.

Conclusions so far:
- Shiney metal flakes in the gear lube indicate near term final drive failure.
- Dark colored gear lube, especially when previous lube changes have been lighter in color, indicates a problem. This suggests that using the same type/color gear lube and keeping to regular lube change intervals may be helpful in identifying increasingly dark lube. (Please DO NOT start an oil thread here.)
- Increasing grey metal fuzz on the drain magnet may indicate a problem. Again, keeping to a reqular interval of changing lube will help identify increasing amounts of grey fuzz on the drain plug. Increasing amounts of grey fuzz is a bad sign.
- The "shake the wheel" test is basically useless in checking for final drive problems. By all accounts, by the time you can feel the wheel move during a "shake the wheel" test, the hub seal will have already puked out the lube. (The shake the wheel test is a valid check for pivot bearing and other swing arm related problems.)

Based on my increasing understanding of the progression of failure of the crownwheel bearing, I would never suggest just changing the hub seal in a case where weeping at the seal is occuring. Too often there is an underlying cause of the leak that is related to the crownwheel bearing.
 

Attachments

·
Premium Member
Joined
·
2,338 Posts
Thanks for this very useful info. If I remember correctly you had completed a "few" final drives at the time you made a video of the rebuild process. You state you now have 50 completed drives. Have you compiled any data from the drives you have rebuilt? Since the video (of which I've lost the link) have you changed the process you documented? And, if so, why.

Congratulations on taking the mystery out of the final drive for so many of us LT owners.

Sincerely!
 

·
Premium Member
Joined
·
3,108 Posts
Thanks for the post Curtis. It's always good to hear about FDs from your perspective.

If a guy had an extra drain plug it would be pretty easy to check the FD for excess metal before any big road trip by quickly changing them out and then topping off the reservoir. Just a thought.
 

·
Registered
Joined
·
4,404 Posts
Discussion Starter #4 (Edited)
ErnieA said:
..... Have you compiled any data from the drives you have rebuilt?.... Since the video (of which I've lost the link) have you changed the process you documented? .....
Compiled data? Not really. (I've had formal training in statistics, nothing that I have documented regarding final drives would meet any standard of statistical analysis. Formed impressions? yes. Excess preload resulting from excess shim thickness installed at the factory is a primary suspect in crownwheel bearing failures. I'll refer you to many of my earlier posts on this site.

I have changed my process in many ways since making the video, there are errors in the procedure but none of consequence to the final outcome of a rebuild done on the basis of the video. Substantively, the method shown in the video works. I give credit to DMAN for first posting the dial indicator method of calculating shim thickness. I have compared the results of DMAN's dial indictor with the method described in the BMW Service Manual using a depth micrometer and the two methods, done carefully, yield similar results.
 

·
Registered
2017 R1200RT
Joined
·
303 Posts
Thank for this work and post Charlie. I have an 06 LT with 14,000 miles. Changed all the fluids at 12K and did not notice anything on the FD plug or in the fluid.

Would you recommend a preemptive rebuild, if yes, would you be able to do it and how much does it cost?

New to BMW's and I'm sorry if I stated anything incorrectly or asked the obvious.

Thanks,
Sammy
 

·
Premium Member
Joined
·
2,338 Posts
CharlieVT said:
Compiled data? Not really. (I've had formal training in statistics, nothing that I have documented regarding final drives would meet any standard of statistical analysis. Formed impressions? yes. Excess preload resulting from excess shim thickness installed at the factory is a primary suspect in crownwheel bearing failures. I'll refer you to many of my earlier posts on this site.
Perhaps I could have been more specific regarding the "data" I was interested in. I suppose could record information from the damaged / defective units and compare to units sent in for "pre-emptive" repairs but showing little or now wear (I'm sure there have been a few of these sent to you). I thought you mentioned in a previous post that you kept that data. I'll dig around and see if you have anything previously posted.

CharlieVT said:
I have changed my process in many ways since making the video, there are errors in the procedure but none of consequence to the final outcome of a rebuild done on the basis of the video. Substantively, the method shown in the video works. I give credit to DMAN for first posting the dial indicator method of calculating shim thickness. I have compared the results of DMAN's dial indictor with the method described in the BMW Service Manual using a depth micrometer and the two methods, done carefully, yield similar results.
Are you using the specs in the manual (0.05 - 0.1 mm (0.0020 - 0.0039 in))? Or do you have another spec you have adopted that works best on your rebuilds?
 

·
Registered
Joined
·
2,176 Posts
Curtis, what's your feeling on "dealer" rebuilds?
I ask this with the belief that I've seen a pattern of posts here, and a rebuild of the final drive on my bike by a "dealer", where a new bearing is installed and the original shims replaced without a proper measurement of pre-load taken.
It just seems like I've seen too many posts in which a rider suffers the failure, the dealer rebuilds is, and it fails again 20-40K miles later.
 

·
Registered
Joined
·
4,404 Posts
Discussion Starter #8
sgroover said:
..... I have an 06 LT with 14,000 miles. Changed all the fluids at 12K and did not notice anything on the FD plug or in the fluid......Would you recommend a preemptive rebuild,......?
2006 model year is pretty well past the "bloom" of final drive failures.
14K miles is really low.

A rebuild at this stage would be expensive road insurance. Ride it. Change the lube every 6K miles instead of every 12K miles.

Don't worry, be happy.

If you get to 30K miles and are still seeing increasing amounts of grey fuzz on the drain plug magnet, you might then consider a rebuild.

That's just my S.W.A.G., YMMV.
 

·
Registered
Joined
·
4,404 Posts
Discussion Starter #9 (Edited)
ErnieA said:
Perhaps I could have been more specific regarding the "data" I was interested in. I could record information from the damaged / defective units and compare to units sent in for "pre-emptive" repairs but showing little or now wear (I'm sure there have been a few of these sent to you). I thought you mentioned in a previous post that you kept that data. I'll dig around and see if you have anything previously posted.

Are you using the specs in the manual (0.05 - 0.1 mm (0.0020 - 0.0039 in))? Or do you have another spec you have adopted that works best on your rebuilds?
Second question answered first: I use the specs given in the BMW Service Manual. I wouldn't presume to reengineer what the BMW engineers have done. I believe the final drive problems are related to fabrication and assembly, not engineering design.

In response to your first question: I had a box full of cut open bearings from both failed drives and preemptive rebuilds. (I eventually took the box to metal recycling, maybe I should have donated them to the Smithsonian? ;) )
Pictures of some of these bearings have been posted here in this forum.
As I learned more, I started paying attention to more things. I note: the orientation of the original bearing before removal, the history of the drive (what the owner reported, e.g. lube leak, vibration, grey fuzz, shiney metal flakes, how far they rode after noticing something wrong, color of the lube, how many miles on the drive, if it was previously rebuilt, etc.). I have correlated my findings on opening the drive and the rider's related history with an inspection of the cut open bearing. (I have concluded you can learn much more from cutting open a bearing than what you can from an assembled bearing, even after through degreasing; trying to assess the status of a bearing without opening the final drive is fruitless). I also have documented what the original shim thickness was so to compare with my calculations. In some cases where the bearing was intact (a preemptive rebuild) I have measured for shim thickness before removing the original bearing to be able to compare my calculations with original shims. In the case of failed bearings, where measuring the original bearing is impossible, I have simply compared the original shim thickness to what the new bearing called for.
By noting spalling of races, roller balls, and retainer integrity (or lack thereof), and correlating the extent of bearing damage to symptoms reported by the rider and drive history, I feel I developed a reasonable picture of progression of crownwheel bearing failure.

What I have started paying more attention to is changes to the race groove in bearings that have not failed. In the past I noted that the race grooves in some preemptive rebuilds looked wider than others, but this is not a change that I have the tools to measure, and in some cases the change is very subtle. (I suppose I could measure the axial play of the bearing before cutting it open and compare the old bearing to the axial movement of a new bearing.) Then I saw a few bearings where there was no pitting or spalling but the groove was worn to the point of having a very sharp edge on one side of the groove. I believe that this wearing of one side of the groove more than the other side correlates with excess shim thickness (excess preload). It was this finding that prompted me to post this new thread; increased grey fuzz without shiney metal flakes and dark lube I now believe to be a sign of bearing race groove wear and an early indicator of eventual failure.
 

·
Registered
Joined
·
4,404 Posts
Discussion Starter #10
fpmlt said:
.... what's your feeling on "dealer" rebuilds?
I ask this with the belief that I've seen a pattern of posts here, and a rebuild of the final drive on my bike by a "dealer", where a new bearing is installed and the original shims replaced without a proper measurement of pre-load taken.
It just seems like I've seen too many posts in which a rider suffers the failure, the dealer rebuilds is, and it fails again 20-40K miles later.
Yes, this has been seen and reported on before. We know of several cases where a final drive has failed multiple times following rebuilds. This is evidence that the crownwheel bearing failures are not just a problem with the bearing, but rather an assembly problem, i.e. excess preload applied to the bearing. Hopefully, all dealers rebuilding final drives now understand this, but it is hard to know what any particular mechanic knows. You can ask the service manager if they checked the preload and followed the service manual procedure, but like the K1200LT, some service departments are known to "blow smoke" ;). There are also many very competent service departments out there, knowing which ones are is the trick; choose wisely.

I have rebuilt failed final drives that were previously rebuilt by "experienced" or "authorized" mechanics. It is, at least in part, a case of "Read the Manual."

Just replacing a failed crownwheel bearing without following the setup procedure as described in the BMW Service Manual is an invitation to repeat failure.

I now suspect that those cases of weeping hub seals without outward signs of other problems, may also have an underlying cause, and recommend that if a seal is leaking, that the seal not just be replaced but the drive opened and inspected. However, I don't know of reports where a leaking hub seal was replaced only to go on and leak again. I suspect that this has occured, just haven't read reports of it. This is one of the points I was trying to make in my original post in this thread.
 

·
Registered
Joined
·
2,746 Posts
Charlie, I have an early '01 with about 30K miles on it. The oil in my FD is much darker and "grayer" than the oil I replace it with at each 6K interval. There are never any "chunks" on the drain plug and the fuzz seems to be minimal. No untoward noises from the FD, wobble at the rear wheel, or leaks at the seal.

I have no "machine shop" abilities of my own and tend to think that those who do have these skills are magicians of a sort. I think you are more of a wizard than just a magician.

Is there anything I can do, without any special tools or knowledge, that can put my mind at ease re: my FD? Can I safely and easily take the FD apart and determine what, if anything is making the fluid dark? I get absolutely lost when I look at the measurement taking processes that you go through during a rebuild.

The oil was dark when I changed it at 12K miles (I bought it with 7,800 miles on it) and has been dark at each change since.

Thanks for your consideration,

Loren
 

·
Registered
Joined
·
4,404 Posts
Discussion Starter #12 (Edited)
wa1200lt said:
.....I have an early '01 with about 30K miles on it. The oil in my FD is much darker and "grayer" than the oil I replace it with at each 6K interval. There are never any "chunks" on the drain plug and the fuzz seems to be minimal. No untoward noises from the FD, wobble at the rear wheel, or leaks at the seal.....
Is there anything I can do, without any special tools or knowledge, that can put my mind at ease re: my FD? Can I safely and easily take the FD apart and determine what, if anything is making the fluid dark? .....The oil was dark when I changed it at 12K miles (I bought it with 7,800 miles on it) and has been dark at each change since.....
You raise a number of good questions, none of which has a good answer. ;)

2001 with 30K miles: If I were taking long trips on that bike, I'd do a preemptive rebuild, but that's just me.

Gear lube going in clean and coming out dark is normal. Some metal "fuzz" on the drain plug is normal.

How dark the lube and how much fuzz presages a problem? Impossible to say. If I say turning really dark quickly is a problem, what's that mean? Pretty meaningless. Some people have monitored the lube by sending a sample out for oil analysis. Just as looking at the color, oil analysis has to be looked at in terms of trend not a snapshot in time.

As a new drive wears in metal fuzz will be generated, and then then amount of fuzz on the drain magnet should lessen over time. If increasing amounts of grey fuzz on the magnet are observed, that may reflect a problem. How much is too much? Impossible to say. If you get a small amount at one lube change and then a lot more then next change, I'd take that as a warning sign.

As far as inspecting the drive yourself, in my opinion there is little of value you can do unless you are committed to rebuilding the drive yourself. The early stage bearing race groove wear that I started talking about in this thread can only be seen by cutting the bearing open.

(Please, I don't want this thread to be construed as a solicitation to rebuild drives, it is not. I still do them but I am not soliciting them. There are a few folks on this board who know how to rebuild these drives and there are a couple commerical outfits that can be trusted to know what they are doing as well.)
 

·
Registered
Joined
·
596 Posts
While others were complaining of thier rears sea/bearing problems , I dove in and proceeded to replace mine.
I had seen grey fuzz but at the time it was considered normal. I also saw small shiny specks, like panning for gold. Noted it but passes it off because they were so small.
I change rear lube yearly.
Then my rear hub seal started leaking, leaving deposits on the wheel.
I replaced the rear seal without pulling the FD. IE replaced it while still on the bike.
It was still weeping and it showed up on the very bottom of the brake caliper as a drop. Having just replaced the brake pads I was not interested in contaminating another pair.
I popped the cover off and sure enough the seal was weeping.
So I pulled the FD.
200 degrees F in the oven, turned it over and the bearing fell half way out, pushed it out the rest of the way with my thumbs.
Cut the bearing open and at first thought That I had cut open a perfectly good bearing. On closer inspection I noticed one side of the race was a bit wider and the other side had the sharp edge. Absolutly no pitting anywhwere.
When putting the new bearing on I found out that 170 degrees is not enough. 190 for 15 min and fridge freezer for 15 min and the bearing dropped on with a click.
Using Dmans method I got 4 good readings. At this point it started to warm up and get stiff so I bailed.
I found that with the new bearing my existing shim would have been .2mm overshimed.
New shims will be picked up tonight
a .15mm and a .4mm making up .55mm.
I am going with .05mm preload.
My wife says she thinks it is sexy to have a man in the kitchen, she did not think that I would be baking motorcycle parts tho.
All she wants is a new cookie sheet. She even helped with the measurements on the counter.
And lastly I really have to thank Curtis for coming along for the ride as coach.More as reaffirmation that I was doing the right thing. It is not that difficult of a job, it is more intimidating if one has not done this particular procedure before.

I will be riding again this weekend.

Many Thanks again Curtis
 

·
Registered
Joined
·
4,404 Posts
Discussion Starter #14
MountianMama said:
.......When putting the new bearing on I found out that 170 degrees is not enough. 190 for 15 min and fridge freezer for 15 min and the bearing dropped on with a click.....
When using oven/freezer to install a new bearing I would use 250degreesF to heat the bearing and leave the bearing in the freezer a minimum of 15minutes. I don't remember what temp I said in the video.
If the bearing stops partway down the crowngear hub and gets stuck, it is annoying and you can damage the bearing if you have to pull it off with a puller.

Glad to hear you got things back together and are on the road. Others should be encouraged by you to tackle the job.
 

·
Registered
Joined
·
94 Posts
I had a crown bearing seal leak on a trip last June. The seal was working it's way out of the housing. Some members suggested it was because I had gone over a 10K pass in the Sierras. I had taken a picture at the summit and noticed there was no oil on the rear wheel then. By that night I was starting to get a leak.

Got the bike home, took the rear drive apart looked everything over and reassembled it with a new seal.

No metal then and today after 2K miles I change the RD oil again just to see whats going on. No metal or "fuzz" on the drain plug magnet, oil was still clear amber color but the drain plug had a little bit of black sludge on it. One wipe of my finger and the magnet was shiny again.

Is this consider this normal or should the magnet be perfectly clean? I have the 17 ball crown bearing in my '99 so it was most likely changed at some time before I got the bike. I'm the second owner since 34K miles. Currently I have 45K miles.

Thanks to the members who would like to respond. Hopefully Charlie might also like to chime in.
 

Attachments

·
Registered
Joined
·
4,404 Posts
Discussion Starter #16
av8trto said:
I had a crown bearing seal leak on a trip last June. The seal was working it's way out of the housing. Some members suggested it was because I had gone over a 10K pass in the Sierras. .....the drain plug had a little bit of black sludge on it...... Is this consider this normal or should the magnet be perfectly clean? I have the 17 ball crown bearing in my '99 so it was most likely changed at some time before I got the bike.
I doubt the leaking seal was due to change in altitude. Unlikely that the vent got plugged to the point that the atmospheric differences pushed out the seal.
My guess it that a very subtle wobble secondary to bearing failure caused the seal to work its way out. This seems to be the way of bearings that wallow out the groove without spalling/pitting the race. i.e. leaking seal but no shiney metal flakes, just grey stuff on the magnet.

Since you have a 17 ball bearing in a 99 it is fair to assume that it was rebuilt. And there's no way to know if it was rebuilt properly or if the bearing was just changed. If the bearing was just swapped out a repeat failure is likely, I've rebuild one FD that had a 17 ball bearing.

I have learned that when you open a drive and "everything looks fine" it isn't necessarily so.

Impossible for anyone to say, but I suspect things are going bad for your 17 ball bearing. I suggest taking it apart, pulling the bearing and cutting it open. Betcha a beer the bearing looks bad.
 

·
Registered
Joined
·
10 Posts
I can attest to no perceptible movement in rear wheel at failure. I can also attest to increase in fuzzy, not shiny metal on drain plug prior to failure. I was in Sturgis last week and 400 miles into my riding when rear drive failed. I had changed oil 400 miles earlier and detected more fuzz on plug than normal but no other indicators.

After unloading bike in Sturgis on Monday and riding a 100 miles or so, I started to detect a slight rumble, 300 miles later....total failure. AAA loaded bike and delivered to Sturgis BMW. They charged me $63.00 to drain oil out and confirm my suspicion?? Sturgis wanted $1,750.00 to replace drive with no other options. Terrible customer support from Sturgis BMW.

I purchased a Dyna Low Rider and rode 1600 more miles without incident. I will replace drive myself and keep both bikes. I was going to sell Harley when I got home but it fills a niche in the stable.
 

·
Registered
Joined
·
94 Posts
Three thousand miles and counting since I opened the rear drive, inspected it and replaced the displaced leaking crown bearing seal. I'm a little suspicious of the last seal installation since I noticed some silicone sealant installed/pressed in between the seal wall and the RD housing. (19 ball changed to 17 ball).

Nothing in Clymers or the BMW manual about using silicone here. One thousand miles to date since I checked the magnetic drain plug and changed the RD oil after the last inspection. No leaks, still bone dry and smooth.

I washed the bike today and just hosed off brake dust from the rear wheel, (finger wipe test before wash) no oil after another 800 mile ride last weekend. LED flashlight inspection looking between the rear brake disk and the rear drive housing is clean and dry after 3K miles.

Just the facts but I'm watching it like a hawk.
 

·
Registered
Joined
·
353 Posts
Thanks for all the good info. I have been just checking the rear wheel on my 05 when it is on the center stand. I change the oil every 5000 kms (3000 miles) and have not seem any noticablty difference in oil colour or fuzz on the drain plug. I now have 85000 kms (53000 miles) on the bike and still no problems with final drive. I was thinking about changing the bearing in the final drive at around the 100000 kms mark as normal maintenance.
 
1 - 20 of 239 Posts
Top