Well......I had the differential rebuilt over a year ago, at that time the shop put a bottle (4oz) of friction modifier in but no lube. Over the course of the year that sucker got moved a hundred times and a bunch of the modifier was spilled out. How much I don't really know. Two weeks ago I installed the thing, filled it with lube but added no additional modifier.
I tried to get away with the abbreviated version of the story but now you get the whole deal.
However, the question is should I try just adding some more modifier (assuming the lube is full since nothing is dripping out)?
I thought maybe because I used the synthetic lube it would be slickery enough without the added modifier. Maybe I was wrong.