My 456 is getting increasingly creaky and I’m having trouble diagnosing the problem. The creak sounds like its coming from the seat tube. I’ve tried swapping seat post (thomson set high) and seat and it makes no difference. It happens mostly when I’m seated but a bit when I’m standing. Crank, pedals and bottom bracket feel solid.

When a pull the seat tube out it is always covered in rusty grease. Could this corrosion becausing the problem? If not any ideas what it can be?

check there are no hairline cracks in or around the welds, I say this as I rode with someone whose frame cracked on a ride and the sound was so so similar to pedal, bottom bracket bearings, worth a check over.

Mine creaks like ****, prolly your post. It started when I began using carbon paste due to a slippy post, if I put just a bit on its noisy as hell, if I put plenty on it shuts up.