Diff Or Gearbox Noise ?

[Wilkie]

First of all this is my first post... so if this is up somewhere else i can't find it. I apologise if it is

I just bought a R33 skyline about 3 weeks ago and noticed that there was noise coming from the back end of the car, and when under pressure or full boost i get the smell of diff oil leaking onto the exhaust. So in turn I went out and purchased a diff put it in and the noise dissapeared ! job done i thought ! i was wrong

About 1 week after it was put in there was no noise and the car was running perfect... So i decided to give it a bit and ever since then the noise came back... now it is really loud andgetting really annoying.

The noise sounds like it is coming from the gearbox but the sound is identical to the sound of when the old diff was in.

I took the car back to where i purchased the diff and asked them to go over it to see if the diff was the problem, 2 mechanics drove the car and both suggested that it might be the gearbox instead of the diff..

When in gear and acceleration is applied the noise builds when more acceleration is applied... but when my foot is off the accelerator the noise disappears completely !

I know the throw out bearing needs to be changed but i doubt this will affect the car so much to make the noise i hear !

I was wondering if i could get some advise on this problem because i do not want to go and buy a gearbox if it is not needed !

any answeres would be awsome