What are the proper steps to take when replacing the rear differential gasket

Don't know why the silicone didn't work... That's all I use!!!. Now, since you're using a gasket, clean both surfaces of 'all' material and install the gasket ONLY, don't use any sealer, just the gasket... Torque bolts to 30 ft lbs in a crisscross pattern... Make sure the cover flang isn't bent!!!!

Install it with the proper torque. You've done it before same thing but with the right tools. Over torquing it can mess up the seal and cause a leak.

Take your time and make sure the surface is clean and dry.