Neutral gear rattle

[Clockwork]

Just installed a TKO 600 in my '69.

Clutch, PP, TO, pilot bearing all new as well. I am getting a rumbling, grinding noise when the clutch pedal is up in neutral, it goes away when the pedal is pushed down. The tranny itself shifts flawlessly and there is plenty of freeplay between the TO and PP.
I was thinking the TO was bad, but I have gone under the car while the noise was present and moved the fork up, down, in, out all around and heard zero change.
I have read that this is common with Vipers.

Any TKO users hearing this same noise??
Could it still be a bad TO??

[cutlasskid]

i have the same problem when i first start the car and let it warm up but i noticed after pumping the clutch pedal a couple if times it goes away so i think mine is bleeding down when it sits.

[Clockwork]

How many miles do you have on yours? I called Tremec today and they said that the TKO is naturally louder than the T56 due to the ways the gears are cut.
I only have about 20 miles on mine, basically just trial runs trying to figure out a speed vibration. So I will leave it as is and see if it clears up after the 500 mile break in.

[cutlasskid]

i have my for 2 yrs now alot of beating in that time