whiring grinding

[chitwnvw]

I have my rebuilt transmission (002) installed with maybe thirty miles on it. And lately I've noticed that I have a whirring-grinding noise. It sounds like it's coming from the transmission and/or CV joints. It's not really loud, but now that I've noticed it, it's all I can hear when I'm driving. It's a strange sound, kind of like two giant stones rolling against each other, but heard from a great distance. It's most noticeable when I am going over 15 miles an hour and when I push the clutch in and take the load off of the engine. Any ideas on what to check?

I just removed my interior, and am really hearing what is going on in back, so I'm not sure if this a new occurrence or just easier to pick up now.

[chitwnvw]

I've recorded some sound of it:

http://home.comcast.net/~toddvoigt/soun ... dnoise.mp3

It's especially noticable at the end...sounds a bit like a train lugging into a station, or maybe a clothes dryer.

[Amskeptic]

If it is a ring and pinion mesh, you will hear it only increase in pitch with the vehicle's speed. Does it happen only under acceleration, or only under deceleration, or all the time? Does it go up with the engine rpm? Is it particularly noticeable only in 1-2nd, or 3-4th? These questions are to help localize the culprit.
Colin