I ran the Mopar modifier in my fresh Power lok and it chattered BAD, tried more, made no difference. Called Cass,Dr.Diff, and explained what was happening and I thought for sure I broke a cross shaft or something and needed to pull it back apart. He said it sounded like the exact same thing he experienced with a Power lok he rebuilt in one of his pickups. He said to drain it and fill it back up again except use GM!! limited slip additive this time before I pulled the pumpkin, and the thing has been smooth as butter ever since. I couldnt believe it either but my guess is the Mopar stuff is formulated for Track-lok and maybe cone style diffs.