Source of washer on magnetic diff plug?
 

After removing the fill and drain plugs on my 915 differential, I inspected the magnetic plug and found a small metal washer that had been attracted. Some metallic sludge was all else on it which is a good thing. I was hoping not to see any metal parts or teeth. I had the transmission rebuilt 12 years ago at 154k miles. I'm now over 201k miles. Is there anything internal to the differential that could be the source of this washer or could this have been a screwup when it was opened for the new transmission. Fortunately there was no nut or bolt that accompanied it.

I dunno, but my vote is it's a screwup.

The only internal washers that I know of are the lockwashers for the bearing plates. These are in the tranmission side of things. I don't know what might be in the differential part.
-Chris

Usually people find a loose needle from a needle bearing! There are small wave washers (6 or 8 mm) on the shift guide and shift fork pinch bolts; they provide a locking action to the pinch bolts. If the washer you found looks wavy when we viewed edge on and has a 6 or 8 mm (center hole) that's what you've got. If you are lucky the washer just fell off the bolt or off the fork after the bolt was removed or during installation and was never noticed. If you are unlucky a bolt with it's wave washer has come loose and fallen off one of the shift forks. The fork may just be being held in place on the shaft by it's plastic "set" caused by originally tightening the pinch bolt. Sometimes the clamp of the fork (where the pinch bolt fits) has to spread open to get the fork to release after removing the pinch bolt. If this is the case a hard shift might loosen the shift fork plus the bolt may be laying in the bottom of the housing. I seem to recall these bolts were brass or bronze so a magnet will not retrieve or attact them. Let's hope a washer was just dropped and not noticed. Jim

The first thing I noticed was how thin and wavy the washer looked. It is approximately 6-8mm. I haven't noticed any shift problems so more than likely that it was just left in the casing by accident. Looks like you've nailed the source.

Thanks

Pretty soon I'll have enough loose parts to build a new car. Last night, I was changing the oil in my 740iL and noticed a spring and broken plastic parts in the bottom of the cannister that holds the oil filter.

Found out I need an entire new cannister to the tune of $300 just for the part. Maybe I should just skip motor oil changes and transmission fluid changes and go through life dumb and happy.