i took a video
https://www.youtube.com/watch?v=gPFYR3ic7Nw
you can hear it from that, it comes on about half a second after I put my foot down, and it basically overtakes the sound of acceleration as that's all you can hear.. it gets louder the faster I go, but only happens in 1st, 2nd and sometimes 3rd... basically under heavy load
I had my mechanic drive with me today and heard the sound, he said it was either the transmission mount or something wrong with the gearbox..
I was leaning towards the transmission mount as well, is that what it is?