Transaxle Noises

Hey,

I hear an odd noise sometimes as I release the clutch and engage 1st
gear on my '91 Civic Si on what I believe to be dry pavement. The
quality of my clutch release seems to be closer to 'correct', as opposed
to either too fast or too slow when it happens, but thats a rough
observation. I guess it sounds similair to the noise my car makes
sometimes when my my tires spin on snow and ice. It is a sort of 'whirr'
sound, maybe comparable to the noise that my car would make in reverse.
It is brief when I hear it; definitely less than a second, and I don't
think I've heard it in the summertime (Wisconsin, USA). Is this anything
to worry about? It doesn't happen everytime I drive, or only when its
extremely cold. The car has ~140k miles on what I assume is the original
clutch.

Mark