So last year started off with me replaceing my slave cylinder in my C5. I also replaced pretty much everything your supposed to when doing that job. When all was done my new slave leaked. Tear down number 2. Replaced faulty slave. Put everything back together still leaked. This time the leak came from the rear main seal. Tear down 3. Using all alignment tools and going step by step from the "book", I put it back together. No leaks. About an hour into my first drive a howeling sound that you can only hear while sitting in the car started. It seamed to be coming from under the dash and above the clutch area. The noise stayed the same whether in gear or out clutch in or out and driving or stopped. Then on one drive with the radio loud because the noise was driving me nuts. I turned down the music to find out that the noise was gone. Next drive, 2 -3 hours with my wife, we were almost home when I said to her how glad I was that the noise went away. 2 blocks later it was back. That was last year in the fall. Since then I had it running once to turn it around to put in the garage. The noise is still there. All my research tells me its the pilot bearing. But I don't want to go through all that work to find out that it's something I've over looked. So if you have any knowledge in this I could use some guidance. Thanks for listening.