Originally Posted by mlempenau
Ok, we will try it again. (It was the computers fault!!) The computer is confused too!!
Can you post some pics of the crown wheel assembly? Pics from both ends, the big round ball bearing (crown wheel bearing) and the smaller tapered roller bearing?
What year is the bike this final drive is off?
From the pics you have posted: there is pitting on the mating surface of the final drive housing. I have not seen this before but this I don't consider critical; I do wonder how it got there.
The foreign object you show I don't recognise. It doesn't look like any part of a FD I am familiar with. It may really be a foreign object.
There is corrosion or something around the seat for the tapered roller bearing outer race in the FD housing. Not sure what is going on there. Can you clean it up a little more and take a couple more pics?
Trying to be helpful. You have something that is different that the classic crown wheel bearing failure. Some later bikes have had the tapered roller bearing spin on its shaft, so I wonder what that bearing and shaft look like.
From what I am seeing on the current pics I wouldn't dare comment on whether I thought the drive was worth rebuilding or not. But I think not.
Also, take a pic that shows the whole FD, I am having trouble getting oriented. I think I am looking at the drive upside down.
I am starting to think that the input shaft that the pinion gear rides on has invaded the space occupied by the tapered roller bearing.
What I have circled on your pic isn't right. It looks like the input shaft has busted through the housing and dumped a thrust bushing or something into the tapered roller bearing space.
Edit added: Yeah, that's it. Your input shaft has come loose somehow and punched its way through into the recess of the tapered roller bearing. The loose piece you found has the marks on one side from where the end of the input shaft was spinning on it. The other side was part of the wall of the tapered roller bearing recess. The input shaft has punched loose that piece of metal which subsequently got chewed up in the bearing or gears.
I don't know of anyone who has reported this kind of failure before.
You need a new drive.