Drive-train/tranny diagnosis?

[Drew Mouton <drew@xxxxxxxxx>]

Hello All,

More interesting problems as I work my way through rebuilding my 
daily-driven '87 325iC.

At the beginning of the week I started hearing a high-pitched, fast-paced 
chirping sound on accelleration from stop up thru about 10-15 mph. As I 
accellerate it evolves into more of a rattle (which I can feel thru the 
center console of the car) then seems to go away as I speed through 20mph 
or so. No noticeable problem at highway speeds.

This seems to only happen when in gear (ie no problems if I rev the 
engine in neutral), doesn't seem to exist in reverse gear, the _pace_ of 
the chirp doesn't seem to change based on speed - meaning it sounds about 
the same at 5mph as it does at 10 - and it has gotten progressively 
worse. 

FWIW, tranny fluid is fine, same color as when I put it in 3 months ago.

I feel like I should know what this indicates, but I'm drawing a blank. 
Would anyone care to make suggestions before I start spending a lot of 
time ruling things out?

Thanks much.

Drew

------------------------------