Bringing this thread back, I was curious how things worked out.
Running a similar setup, with an ACT HD PP, Street and strip clutch disc, and lightened flywheel, with an OEM TOB. I recently pulled my transmission to address a similar sound; rattled pretty badly when idling (sounded almost like a badly running diesel) with the clutch pedal released (so the clutch engaged). Would cease when the clutch pedal was pushed (so the clutch disengaged). Running a fresh OEM TOB, so I knew that should not be the problem, although there was a bit more play on the shaft that the TOB rides on than I was expecting. I was also experiencing some fairly significant vibration at times during acceleration. These symptoms led me to believe the input shaft bearing(s) were suspect. Back to Greg V. to order replacement bearings...
Pulling the transmission, I did indeed find that the bearings exhibited excessive play (I could take the input shaft, shake it and replicate the knocking sound I was getting).
I went ahead and pulled the old bearings, which was pretty simple. It involved punching out a welch plug in the tranny case, then punching out the old bearing assembly. After, use the old bearing case to drive the new one back in place. Use sealant on the welch plug, and drive back in place. The other bearing required a 6" three leg gear puller. Then a trip to a local shop with the new bearing and input shaft, and $20 later it was pressed on with a 20 ton shop press. I popped out the old input shaft oil seal, and drove a new one in before reassembly of the tranny.
After reassembly of the transmission, the input shaft felt much better. Putting it all back together, I tested the remedy on the race track the next day. What I found was the vibration was gone, and the tranny was MUCH quieter, BUT... I still get the rattle to a certain degree; What happened?
What I believe the source of the noise I'm experiencing now is, is the ACT HD Street and Strip clutch disc; specifically the springs. From what I have read, these units have a tendancy to be noisy, and rattle, occasionally breaking springs. The only way to really verify this will be to pull the tranny (yet again), and replace the disc with a B15 disc. I believe this will cure the rattle for good.
Hope you were able to chase this down, or at least this thread will provide some help to someone else.
Darrin
Search parameters: ACT SS disc, street and strip, clutch, transmission, tranny, noise, rattle, knock