I would try running it up to the point of the noise, hold it steady there, and push around on parts in the top end with a wooden dowel, or something similar, to see if there's something loose enough causing some vibration that might be minimized with the pressure. I'm thinking of a 66 I was having problems with, was binding somewhere, I oiled and oiled in all the oil holes and it seemed to spin better briefly, but never correctly, then Leon pointed me in the direction of the nose end of the machine and that's where the problem was, fixed it with a gentle pry with a screwdriver.