The consensus among many BMW folks is now centering around the amount of preload between the big bearing (wheel/hub side) and the cover and the fact that the sub assemblies are not correctly shimmed at the factory. There is also a crew that follows that the bearing itself is the culprit. (BMW's replacement bearing has a different number of rollers as compared to the original ones. Again, I don't know about the EVO designs.)
I know when I took mine apart (using a borrowed BMW shop fixture to check it all) the measurements didn't add up.
This is what I do for a living. I build transfer cases, differential units and PTO boxes all day long so I know a thing or two about setting pre loads.
My take on the whole matter is that the bearing just isn't big enough to take all the load, especially when the BMW riders seem to over load their bikes on a daily basis. (Anyway I do.) This and a bearing that is taking pretty much the entire weight of the bike and a lot of angular thrust when you are on the throttle coming out of a corner hard makes me wonder how the last as long as they do.
Dealers charge about 350-450 to do the rebuild when you take the final drive unit to them and lay it on the counter. The actual parts run about 80-160 dollars depending on what you replace. If the owner is one of those people who can't/won't do it themselves..well then..you will need your own, personal jar of Vaseline along with never knowing if the preload was set correctly or they just reused the existing shims.
