This is kind of far out, but this board is so good, I'll give it a try. My gandson's Volvo has a "rattely" sound that comes as follows: With my head down between the exhaust manifold and the fender, there is a loud, tinny, vibrating noise that comes either from the transmission (automatic) or the exhaust system. It occurs when the engine is reved up to about 2500 rpm; it isn't there below that speed and disappears above that speed. Is it possible that there is something loose in the catalytic converter? I don't know what there would be in the transmission that would cause that noise.
Anybody else experience such a noise?