shreiking turbo
 

I've noticed over the past couple of months that my turbo occasionally makes a pretty loud shrieking sound on spooldown. Sounds like metal to metal shrieking like a bearing going out or something. The turbo seems to spool just fine and I don't detect much shaft play (there is a tiny amount, not sure how normal that is because this is baby's first turbo). I assume this isn't normal, but i'm curious as to what i can do about it? Does a rebuild usually replace all the bearings?

Yup, a rebuild kit will replace everything except the housings, CHRA, shaft, and blades... but with only a little shaft play and (I assume not smoking), you might want to look at something else. A turbo that needs a rebuild should always smoke at least a little.
You're 100% positive it's the turbo?

Yeah, no smoke at all and no oil in my IC pipes. I can't think of anything else on the car that would make that noise at that instant. I'll see if i can catch a video of it. i think my phone captures small videos.

In/out shaft play is normal, and a little is acceptable. Side/side shaft play occurs as the bearings wear down and the shaft can move around more freely.

Don't mean to alarm you or anything, but when one of our fire engines did that it was just after it had ingested a small bolt.

there's no percussive sound to it at all though. it's more like dragging your fingernails down a chalkboard.

the turbo is probably due for a rebuild anyway with the miles that are on it. Where would i look for a rebuild kit for a stock Greddy kit turbo?

if its only on spool down , then it may be a faulty BOV staying closed on throttle off...causing compressor surge which sounds like that...just a thought.