The intermediate steering shaft should only clunk when you turn. My Wife's 01 Bonneville SSEI did the clunking, we had the intermediate steering shaft changed and really it is not a bad job. The NEW intermediate steering shaft is also making a clunking sound, GM has had an issue with them for years. The issue is that they use a nylon type of spline inside a steel housing and the nylon just does not hold up. May not be nylon, but a plastic type of spline. I took my old one apart and looked at it, hopefully they have improved it.
