So I've had the 04 for a week now, and have been starting to do all the usual stuff of fluids and such. Did the transmission filter and fluid tonight, and went off without a hitch. I should have known not to go further...
I figured I might as well do the diffs as long as I'm dirty. Do the back one, no problem. Oil looks great and not much on the magnet. Do the front one, and the oil is much darker. Didn't think too much of it, as it was the same on the 00 for me. I shine the flashlight up and something catches my eye on the edge of the drain hole. I stick my finger in, and pull out the following:




OK...any thoughts guys? It is an 04 with 76K and been on female driven grocery getter duty it's entire life. Stamped on the top is "12 . 9" and also "u" with three letters or markings after it but scratched so I can't see it. It looks to a clean sheer of the bolt, with a couple millimeters of thread left on it.
With fresh fluid and a cleaned off magnet in there I'm thinking I will run it a few days, and drain it again to see if I find anything else. No big shavings in the fluid or other chunks, but I have a sneaky hunch there might be another piece of that lurking in there. I thought I felt something with my finger, but was too far away, and I didn't feel like sleeping on the garage floor because I got my finger stuck in there and the wifey was already in bed and my phone was hooked to the stereo for Pandora
Leave it to SNAFU to find odd stuff like this...

 

No strange funky noises when moving off? clunking, etc?

 

Looks like the head of a bearing cap bolt. It will hold together until it doesn't. You really should pull it apart.

 

Fast forward to 1:57 in this video. See anything familiar? I agree with the above poster. You already drained it, time to pull it.

 

Its prob been that way since new.
I would leave it if it were me.
I have figured out to never buy a used car that was only driven by a woman, thats worse than a teenager.

 

^what Spike said. I have three sisters and only seem to date blonds.

 

No noises, no clunks, no hums....nothing seems odd. Anyone have a front diff laying around where they could match it up for me by the numbers or markings?
Also, I could always swap the diff out of the 00 I have if the same part. Would hate to put one in with double the miles and 4 years older if indeed this is a factory part left in it, and likely held by the magnet for all those years.
If it is the head to a bearing cap bolt, what would cause this to happen? Would have had to be a pretty traumatic event I would think. This was a southern Cali truck most of its life, so not likely stuck in deep snow, and not a mark under anywhere.

 

Doesn't look like a bear cap bolt head. It looks like one of the bolts that secures the ring gear. That would be odd if one of those sheared off though.

 

One bolt down, so you have a weak spot in the diff. If it were mine, I would open it up now instead of waiting for it to fail and cost you bigger bucks.

 

^^^ That's what I would do too. I can't imagine tearing down one of these diffs would be terribly difficult. It's put together like a Ford 9", and I've pulled apart a few of those.