Probably bad u joints. Jack it up and get under it and look at em. Get back there by the rear end and and twist the DS and listen and look. Make sure the noise isnt coming from the rear end. Its probably the u joints. Does it make any noise while driving normaly? Did you have a vibration at a certain speed?
i dont think its my rear end cuz i got ym gears done maybe 2 months ago and done by a respected place but anyways sometimes i get alil vibration but nuting serious. and it makes a lil grinding sound wen coming out of first but for like a quick 2 seconds and it has made this noise even before i did my gears its been doing it since i baught the car