I'm tired of moaning...
 

The rear end on my GSL is getting louder it seems, I did the rear oil change using synthetic gear oil, but, it still moans, I see that there are additives specially for LSD units, and the write ups almost demand that you have to use only LSD oils to make the LSD's work,,,here is one add; K & W Posi-Trac Limited Slip Differential Gear Oil Treatment
""""can just the additive do the trick????
I cant seem to find just a pure 2 quarts of LSD gear oil, only additives,,,,,

In the spring of 2002, I replaced my '85 GSL's LSD fluid with non-synthetic (see your manual) and added GM's LSD additive, per the instructions. All chatter and most noise went away. There are 215K miles on the LSD and it saw track time each of the last two summers since the change, with no issues.