So noticed this today. Only happens (or I can only hear it) at idle. It's a thump more than a knock i guess and it happens sporadically while I'm sitting in my driveway at idle. it stops when I depress the clutch pedal.

Throwout bearing?

 

I've been getting this thump similar to your description. I didn't know if it was from the engine or the transmission. Never was able to find out. In for answers, though..

 

Hlong has yours been going on?

 

I've noticed it about a month ago. It comes and goes, though. It'll do it on certain mornings when I'm waiting for car to warm up, and some mornings it wouldn't do it. This goes for idling anywhere, at operating temperature or not.

 

It could be the throw out bearing. I'm more suspicious if your car has it's original clutch.

--Spike

 

as far as i know it has the original clutch
but like i said it still shift fine. and drives fine.
it just makes that noise. that stops when i push the pedal in

 

This sounds like the throw out bearing to me..

I also have this- had it since I got my z with 30K and now I'm at 50K. Clutch is still strong, from what I've researched it common and doesn't hurt the car nor effect performance.

 

so dont worry about it? or wait till it ***** the bed? im hoping by this time next year ill be LS swapped so it puts me in a weird position as to whether or not i want to spend money on it