This is just an explanation of what causes the chatter and possible solutions for it. Thought it would be a good read to have available. Some gear lubes come with additive already in it(severe gear) and some may not requiring the need to add some.

Diff. clutch chatter tech bulletin

 

As you know Heath i used severe gear and still had to add the friction modifier

 

For some it's just never enough
There have been some that have needed to add it. Hope it solved the problem?

 

Absolutely my diffs are very happy now

 

Good info