[86Toy05Taco]

I'm not sure how or if the bell housing is sealed (I need to become more mechanically educated!), but my theory is that in my case, if it were a problem with the actual clutch disk, pressure plate, etc., that the clutch would chatter all the time. The fact that the problem goes away and moisture seems to a factor would suggest to me that it may be an issue of water/condensation on the clutch plate. Maybe someone with more mechanical knowledge could shed more light on the situation...

I found the below post awhile ago when I was looking into this issue that supports the moisture theory. It was from some BMW message board (can't remember which one):

"I have a 04 325i and started experiencing clutch chatter at around 4000 miles. I noticed that it only occurred when the car sat in the rain for a period of time. I brought the car to the dealer and by time I got there it was warmed up and the chatter was hardly noticeable. So I decided to fix it myself. After some investigating I came up with a solution. On the hood there is a vent, which takes in air for the interior. When it rains water runs into this vent and 2 ducts, 1 on each side are used to drain it. These rubber ducts are at a 90 deg. angle and send the water towards the firewall of the car. What must happen is the water flows down and somehow gets into the clutch assembly. If you remove the ducts and rotate them 90 deg. so that they point towards the inside of the wheel wells it will solve this problem. Its only takes a few mins. to do this. I now have 9000 miles on the car and it has been in rain, snow and cold weather and I still have not experienced clutch chatter since."