grey and metallic = metal shavings = bad, very bad. it'll be hard to tell exactly what is wrong with it, just that something IS terribly wrong.
It's in your bearings, gear teeth, and essentially everywhere. Slowly grinding away at 1,000's of RPM. Sure it works now, I wouldn't trust it for much longer. MAKG is quite correct, the first thing to look for is another T-case. Your living on borrowed time.
After getting a replacement and installing it, then I'd crack it open if your still curious.