The intermediate steering shaft is what connects the steering column to the rack, it's not really a suspension part. GM did come out with a kit to lube it, but there's instructions online on how to do it yourself, a search should uncover them. The clunk while turning could be a lot of things, I just mentioned where I would start. The CVs could very well be the problem, although if they're not leaking, it's less likely. It could also be a ball joint or a tie rod end.