[richtazz]

My 90 Grand Prix (sister car to your Lumina, mechanically identical) had the rear sway bar and it rattled like a ticked off diamondback. It's not a dangerous situation, just an irritating noise. I took the whole sway bar off and had no issues. The only thing it does is limit body lean in extreme cornering. The ponderous part is the effect of the rain. All I can think of there is that the rain lubricates the bushing and keeps it from squeaking until it dries out.