Noisy rearend 69 barracuda 318 car

50 years ago I was hich hiking to Alaska and got a ride in this box truck that had a real noisy rear.We stopped at this garage in this place out in the middle of nowhere and the old guy who was working there suggested we put in a LB of powered graphite to quiet it down.It worked and we continued for 1200 miles up to where they dropped me off without any noise or problems . You might want to try a Moly additive like Cal Guard . I use it in all my standard transmissions and my 71 chevy trucks rear and my shaft drive motorcycles rear ends . It coats the gears and keeps them lubed.