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.