This is a kind of "rattling" noise that is coming from under the car, between the flywheel and tranny area. This noise has been there for over 4 yrs. and it never gets any worse. 2 yrs. ago , I seperated the engine from the tranny at the flywheel , started the car and the noise was still there. It doesnt have the noise at all whenever you first start it up, just after it gets warm. I have done the stethoscope thing all over that engine and tranny.It just sounds like a heat shield "rattle" but its not.I am open for ANY suggestions that might be out there. The car runs like a beast and is in excellant shape.Sooooo! Get those thinking caps on please. Thanks Everyone.

my friends olds 88 with the ln3 is doing the same thing, we just ignore it. i personally think it might be an exhaust shield rattling or the cat maybe.

the manifold shields do rot out and rattle. Put a stainless hose clamp around mine and all is quiet.

Does it sound anything like this?

http://media.putfile.com/Idle88

ofnarcr4 That is what my noise is like on my bonny.