The unknown g20 gremlins
 

I have a 91 Chevy G20 with a 5.7 in it. When I drive it it makes a clunking sound on the rear right side. I've changed out the break pads I've put new I joints on the drive shaft and it still does it. This is the part that stumps me after asking for advice from some mechanics. When I come to a stop its noisy when I start out driving it gets less and less noisy. When I go in reverse it's the worse. When I'm going forward and when I'm stopping and I gently apply the emergency brake while I'm moving it goes away. But nobody and no repair had figured it out. Can someone please help.