I think i know what you are talking about. If you have managed to get the lock ring off, and its the actual chassette that wont come off of the hub, I had that problem a few days a go, i could'nt find any way of getting it off it was like the previous owner had mulered the thing with a hammer. The only thing i can say is to PULL IT!! VERY HARD, the heavy handed approach, well thats me any way. I did for about ten minutes and it finally came loose, and when i went to put on the single speed it slotted on lovely and when i did it up with the lockring it was tight as a tiger. Have you removed this part forget about the yellow word im talking about the lockring If you have got it off then PULL of not PLEASE DONT PULL!. it may rip the threads of the lockring and hub thread