Chuck,
Try this. I had the same problem with my nine inch. I used about three feet of rubber tube that feed into the bottom of a tilton remote brake reservoir. I mounted the reservoir about a foot and a half higher than the rear end on the inside/back of the trunk. Whne the rear end pressurizes , it will push
oil up the tube into the reservoir and when the pressure is relieved it will drain back into the rear end. The whole set-up cost about $15.00. The plus is I can add
oil to my diff any time I want through the top of the reservoir.
--Mike