Originally Posted by CharlieVT
Do I understand you to say that the aluminum component spins smoothly in the hub? The aluminum part that the tapered roller bearing is seated on spins freely within the hub that the crownwheel gear is part of?
I didn't understand that from your earlier posts, you did say everything was turning smoothly, but I didn't imagine you were referring to the components of the crown wheel assembly itself. Yikes!
THAT IS the failure mode described in BMWON. Verrly Instersting... Yours is only the second one that I have heard of, the article in BMWON being the first. And I suspect oil leaking out of the wheel bolt holes is an early indication of this failure. I feel silly having first suggested that too much oil would be the cause of oil coming out the bolt holes; I just remember noting that the bolt holes were drilled all the way through the hub during my past assemblies and didn't think about it further; your predicament and findings have helped understand these drives further. WOW!, BMW has sure managed to build a final drive that can fail in so many ways.
With this new understanding, (what I think I know
) I would speculate that any oil leaking out of wheel bolt holes is an indication of impending failure of the crownwheel assembly. I would now say that any oil coming out of the wheel bolt holes is an indication that something is wrong with the crown wheel assembly and should be investigated.
I guess I was not very descriptive my earlier posts. Since I did not have another unit to compare to, and the pieces moved SO smoothly, I thought that was the way of the beast.
I was troubled though, why you would have a bearing on the end AND have one internally.
Anyway, I have disassembled the unit, which was quite easy. Just take a punch, put it in one of the wheel stud holes and tap(somewhat hard, but not real hard) while spinning the aluminum piece. Comes out with no heat or cold.
The unit is very smooth, but not obviously damaged.
I have reassembled the unit using the suggested Loctite.
Glass beaded both pieces(hoping to ruff them up so the Loctite would have something to adhere to) cleaned with solvent and drilled three holes though the steel hub and into the aluminum piece and put in small pins under the big bearing race. Waiting on things to dry before putting the bearing back on.
Was in a big of a hurry (not sure why...) and forgot to take pictures...rats.
You are correct in thinking any oil coming from the crown holes would mean that the two pieces have separated.
I have rode that bike for 10years and know it pretty well. I could tell when that "infamous" bearing everyone was talking about was going bad a couple years ago. Checked the drive oil and found metal flakes that reinforced my "feeling"
With this problem,I had no idea this was going on. My only clue was when I changed the final drive oil, it was really black.
I'm not sure it would cause a catastrophic failure with out some kind of sign. I think more of a problem would be decreased oil in the drive reservoir. The oil would "leak" into the aluminum cavity and there might not be enough to lubricate the ring and pinion good enough (over time...)