A while back I posted about the urethane bushings in my Street Lynx 4 link. They sent me new bushings ...free... I replaced them and I kept hearing grinding noises when turning at slow speeds. We re-positioned the mount tabs on the axle for the upper bars after loosening them and hooking the link bar to it then raising and lowering the axle with a transmission jack. Not exactly rocket science but we were able to see very easily where we needed to place them for maximum efficiency/lowest stress.
When complete I didn't even back all the way out of the garage and was hearing that same terrible grinding noise. The kind you just know there is a grenaded pile of metal chunks waiting for you to find them! We called the guy who rebuilt my pumpkin. EVERYTHING in there was brand new. He said the slip gear lube additive wasn't working properly ,put two more bottles in. I'm thinking this is not going to magically weld all those metal chunks back together! Amazingly, there is no more noise in the rear end. Who would have believed it?

good to hear it wasn't catastrophic failure causing the noise.

Hopefully these weren't the gears I gave you.

Clutches will chatter with wrong friction modifier. That stuff is to help them slip not the contrary. I used the Mopar stuff in my Spicer equipped 8 3/4 with new Clutches and it chattered very bad. Added another bottle and no change. Called Cass and he said "oh yeah I had the same thing happen when I put new Clutches in my truck,dump the Mopar stuff and use GM lsd additive". Been fine ever since.