Diff Fluid change

Changing the front and rear fluids today. The front drain plug didnt have a brass washer on it(original fluid) but the fill plug had the crush washer. I have new washers for all the front and rear plugs. Do I put one on the front drain or not? Also got the 80-90 GL4 oil, but does it require a friction modifier to be added?
Didnt remember reading so. Just want to make sure. Getting old suks!! Thanks!!!!! Ron