Thank you for looking - Are these bushings filled with silicone or do the bolts go through them into the back cover and through to the fluid. My wife's car seems to have a leak through the right (single bolt) one. (Not a picture of her actual car but a screen capture from a YouTube video)

 

They’re just rubber bushings like what you’d see on a control arm. They are supposed to cushion forces from the rear differential. No fluid can leak from them as the bolt that goes into the differential case is not submerged in fluid. It’s probably coming from somewhere else.