My 98 C70's moonroof started rattling, really, not squeaking, and it was driving me crazy. As an engineer, I hate any noises in a car that aren't supposed to be there.

So, I removed the glass and then reattached it, trying to push up on it, to recreate the rattle. I noticed that it seemed to becoming from pins on either side that engage the extension mechanism. I didn't have any felt tape around, but I had some grease, which I used in the cradle area where the pins were bouncing around. It's been a couple months, and no problems. Even if I have to do it now and then, the silence is very nice.