I just don't know what it could be otherwise, it made a similar noise before i put the new box in and when i put this new box in i used brand new ARP flywheel bolts, thrust bearing, clutch and got the flywheel machined in an attempt to eliminate the problem.. I didnt get the spigot replaced even though i supplied him with one because he said the one in there was in really good condition anyway because my motor was only rebuilt about 10,000-15,000km ago.. I can't replicate the noise when the car is not in gear and free revving, it will only make the noise when the car is in gear and under moderate to hard acceleration or high RPM and when it makes the noise it sounds like its coming from next to me (the gearbox).. The noise is a really really loud screaming/screeching noise and only occurs under the conditions as i mentioned before and its driving me absolutely crazy.. Aggggghhhhh!!!