yiipi

Hi 2 u all. I have problem with roaring/wining sound in my rear end. When the car is in motion and when it's on load sound does not exist, but when I pass over ~100kmph and put car in neutral with or without pressed clutch I got this roaring sound. Also when I start moving I got some kind of knock sound in rear end. My subframe is on solid poly bushings but I was getting these sounds before changing these bushings. Any idea what is producing sounds? My chassis is S13 with CA18DET engine and 5 speed manual transmition with open diff. Tnx in advance.