It's an aluminum Thomson Elite 27.2mm seatpost in an aluminum '04 TCR with no shim.There is no removable collar, it has two built in bolts on the frame. It's not slipping, it's just creaking. It's definetly at the post where it enters the bike - not the rails. I've tried cleaning it really well, applied shimano grease, spit (works temporarily), and diferrent tightnesses (if that's a word). I actually overtightened one post and dented it slightly. I now have a brand new post in there and it's still creaking. It's just annoying as hell! What else can I try here? Loctite, plumbers tape, different grease, I dunno...