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Discussion Starter #1
I was thinking about this on my way home from my paying job this morning. I see alot of talk about replacing bearings. Is it the material they've used or the actual design? I have a custom gunsmith shop and have lathes and a mill. I can find better material and make bearings. Has anyone tried this?
If it's a design flaw, someone is bound to have an idea. This is going to require more research.
 

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I don't know if there is any one single cause. What is needed is a control study and that is going to be hard. There seems to be a group who think it is a lube problem and another that think bearing/design flaw. I am in the lube group and run Lucas products in everything I own, but I have also purchased a spare final drive from a company that trikes LT's.
 

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Another thought on why some fail and some don't is improper assembly or preload adjustment.
1) During assembly when the bearings are installed they maybe getting pushed on the outer race as well as the inner race. This could cause small indents in the bearing races.

2) Preload adjustment: To much preload could cause the balls to indent to the races slightly. This may be agravated by shipping with bike weight bearing on the rear tire. Bearing is not turning so that any bumps would also transmit load in constant location.

Roy
 

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cmattingly said:
I see alot of talk about replacing bearings. Is it the material they've used or the actual design? ....
If you do a through reading of all of the postings, it seems to be related to assembly problems. I do not think that the bearing has changed from the 99 model year LT.
 

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Discussion Starter #5
So properly installing replacement bearings with ones that have not been previously installed might be an answer? Are there incidents of FD failures after an initial failure, and a new FD had been installed? (lightening striking twice)

Back to the lube aspect. I replaced all the oil in my tractor with Sheffield (sp?) oil and noticed a huge difference in running temperature. It was so much better with Sheffield's oil. I know there's 1,000 oils out there with just as many opinions. But I may try that.
 

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Are there incidents of FD failures after an initial failure, and a new FD had been installed? (lightening striking twice)

I had the original FD fail at 33,000 miles. It was replaced with a completely new unit by a BMW dealer and that one failed at 49,000 miles. Again replaced with a new unit and am now at 75,000 miles and still going. Both were replaced at BMWs expense.

Bob Schrader
'00LTC
 

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I spoke with my mechanic this past saturday .asked him about the FD problems and what he thought was the cause for them. He stated that alot of them he saw were trailer pullers /some he felt were clutch slappers and the fact that when he recieves new bearings from BMW') the source of the bearings has been from several countries / not always from the mother land! This leads me to believe that some of these inferior bearings are placed in new bikes during production as well as repaired FDs.To sum it up / just like many other companies throught out the world BMW is trying to save pennies through cheaper suppliers and we as consumers get screwed :( :(
 

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You can scan the threads and see that few rear bearings have failed in LTs towing trailers.

Not sure what a clutch slapper is?

If you need someone to diagnose why something has happened to your LT, you might think about asking a different BMW mechanic.

So far, no one knows why the bearing fail. Anyone who is asserting a fact about it is simply guessing.

Enjoy the nice wx.
Bob, 0hOh LT
 

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cmattingly said:
------------------------- I have a custom gunsmith shop and have lathes and a mill. I can find better material and make bearings. -----------------------------------------------
You can MAKE BEARINGS???? This I gotta see. Ball bearing manufacture is an extremely involved, VERY high precision venture, with balls and race contours measured in microns, not thousandths or even ten thousandths of an inch. Just the race and ball grinding operations are leagues away from what any machinist, tool maker, etc. could ever hope to even think about, requiring equipment costing hundreds of thousands of dollars. Even the inspection/measuring equipment is way out of reach for just about any individual.
 

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Discussion Starter #11
When I first wanted to make barrels with integral sights and ejector rod housings, someone asked the same question. My response was "if someone else is making them, then I can too." No, I haven't attempted to make bearings yet, but someone is making them. Unfortunately for us, not very well or we wouldn't be talking about this. Only thing I can do is try to do better than them.
 

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dshealey said:
You can MAKE BEARINGS???? This I gotta see. Ball bearing manufacture is an extremely involved, VERY high precision venture, with balls and race contours measured in microns, not thousandths or even ten thousandths of an inch. Just the race and ball grinding operations are leagues away from what any machinist, tool maker, etc. could ever hope to even think about, requiring equipment costing hundreds of thousands of dollars. Even the inspection/measuring equipment is way out of reach for just about any individual.
Reminds me of a quote from the movie Fast Times at Ridgemont High:

Jeff Spicoli (after he wrecks Jefferson's car): Relax, all right? My old man is a television repairman, he's got this ultimate set of tools. I can fix it.[/QUOTE]
 

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Discussion Starter #15
Hey guys...

Before this gets ugly with replies and questions about my abilities as an engineer/machinist/motorcycle repair dude, I just want to clarify that the original point here I'm trying to find out is if there is one dominating cause for FD failures. Apparently BMW refuses to admit there is a problem. But with all this experience on this board, I'd like to take a proactive approach about it and gets some ideas. I'd rather do something about it now, than be stuck out in BFE with a new membership card into the FD Failure Club. It's a machine folks, someone designed the dang thing. But that doesn't mean we can't tweak it. Come on, you've never changed anything on your bike to make it better.... One of these days someone is going to come up with a fix for it and everyone else is going to say, "I wish I'd thought of that!"
I probably can't make a bearing on my equipment. Maybe the aircraft parts manufacturer right down the road can. If not, who the heck can make a decent bearing? Is that the whole problem? Is it the oil? Who's done a study on the different lubricates to find out? That's why I came here to ask y'all! It was not my intention to come on and boast of my capabilities, but to engage in conversion with some experienced and knowledgeable people.
Thankyouverymuch (done in my best Elvis impersonation).
 

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Re: Hey guys...

Nah, it ain't gonna' get ugly - it's just that this has been discussed about - oh - maybe ten thousand times over the years by some extremely qualified engineers, metallurgists, bearing specialists, oil engineers, etc. Bearings have been carefully examined for all potential failure points and sent for analysis several times. Some have failed at 5K, many others have lasted much longer. There are several members (including myself on my first LT) that have gone well over 100K.

The conclusion is: There is no conclusion

Collectively as a group we have not been sitting on our asses. Well, maybe I have - but it's part of my job description.

I can guarantee you that the combined engineering expertise of members on this board is at least equal to and probably far surpasses anything BMW has. Yeah, they're THAT good.

Plenty of suspects but no smoking gun.

Personally, I think the Butler did it....;)
 

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Re: Hey guys...

cmattingly said:
Before this gets ugly with replies and questions about my abilities as an engineer/machinist/motorcycle repair dude, I just want to clarify that the original point here I'm trying to find out is if there is one dominating cause for FD failures.
I have faith in ya, man! And thanks for looking out for us.

Come to our RTE tomorrow and bring weapons.



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Reminder of great contributors

Entertaining thread, this one. :)

I am reminded that I waited for years for someone to come up with a way to measure for crown wheel bearing preload without the BMW special tool. As a service to those who might consider rebuilding their own final drive I will refresh the collective memory here that it was "Dman" who posted the techique that requires no special tools and is elegant in its simplicity:

http://www.bmwlt.com/forums/showthread.php?postid=118116#poststop
 
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