We have a 2004 Bonneville SE which has a repeating clunk/rattle in the front end when driving down a slightly rough road. The car has 28k miles and has had 2 replacement steering shafts, a left strut and mount, and a rack and pinion replacement. We get no noise on turning the wheel. Does the steering shaft problem ever cause a noise when driving straight and not show symptoms on turns? The dealer has been cooperative but doesn't seem to know where to go next. It seems like we hear it less when the vehicle is cold and more when we have driven it some distance and warmed everything or when it is warm outside. We never hear it on a smooth road. I think I can feel it a little in the steering wheel. I sure would appreciate hearing anything from anyone with a similar problem.

I'd say take it to an independent front end shop. Someones gotta get their hands & eyes on that whole front suspension. Get the car up on a lift. They should be looking for anything loose, any bushings that are worn etc. Usually those clunk noises are from metal to metal contact where there shouldn't be metal to metal contact.