Thrust bearing went on my supra. Was told that its got nothing to do with driving hard, its just a bearing, sometimes they go, but its just a noise so don't worry a great deal...
Also, I was told when the thrust bearing goes, putting your foot on the clutch shuts up that noise all together, because there is pressure on the bearing so its stops making the noise, which is exactly how the supra acted and the opposite to how this is acting.
The difference is, when that happened, the noise was always there, this has stopped again this morning... I would be happy to know it is just the thrust bearing though, cause then it would be a $20 - $30 fix + a few hours on the weekend... I'm just a little concerned it has something to do with some other drivetrain components, when my mate had a listen the other night, he said it seemed to be coming from further back... he may have been mistaken though, doesn't know much about cars, he thinks skylines are lines in the sky....