Has anyone heard of removing the stock lst diff grease and replacing it with silicone diff fluid? is this a good idea? thanx. also what weight of oil?

Yeah you can do that.

I put 10,000wt oil in both front and back seems to be good enough for bashing around. make sure the blue seal between the ring gear and the diff cup is in good condition. And only fill up to the cross pins.

Also a good thing to check is the shimming of the diffs. proper shimming will make the diffs last a whole lot longer.