I posted this in LT1 tech also...I forgot about the section till after I had already posted...oh well...

I had my clutch replaced right before the new year with a Spec II and the bolts that hold the PP to the Flywheel were strecthed so I had to get some new ones. My mechanic used some lock washers on those bolts but I don't recall him using any Loc-tite. Over the past month I've developed a rattle from under the car and I figured by y-pipe bolts are loose so I crawled under the car tonight and cranked on them to see and they were a little loose but not much! So I cranked the car up and the rattle was still there...and it has gotten louder and louder over the past month....is there a possiblitilty that the PP - FW bolts have backed out and that is causing the rattle? I put a screw driver up the the front of the tranny/bellhousing and put my ear to it and it seems to be coming from there! Any ideas fellas?

 

I just did an M6 swap, and I also noticed that the tranny rattles. While in nuetral with the clutch engaged, I can hear what sounds like a can of marbles. Okay, it's not quite that bad, but it is noticeable. When the clutch is disengaged, I get no marble noise.

Now, back in the day when I drove transport trucks, I noticed that they also rattled when the clutch was engaged tranny in nuetral.

My tranny is rebuilt, with new input shaft, and new counter shaft. Inside the car, there are no unusual noises; the tranny sounds and feels fine, so based on this I'm assuming that this noise is not abnormal.

Maybe you've just become sensitive to it, because you are worrying about it.