I had the TSB on the rear differentail and limited slip done about 4 months and 15k miles ago. I was fine, but I notice that the chatter is starting all over again, just as it did the first time.

I think that they did everything at the shop. They did not use an additive because they went with a synthetic oil. I think that this is not right, the bulletin says to add the modifier.

What would you do/suggest?

 

Add some modifier.