I used a non-synthetic Valvoline gear oil(probably 80/90) and that exact 4oz bottle of GM posi fluid you mentioned, although I didn't have to use the whole bottle. Can't remember exactly how much. I think the GM bottle mentions the mixture ratio. Hopefully the simple fluid change solves the issue for you.
Amazing how much there is a difference in oils....Changed out the Lucas and put in Brad Penn gear oil, non synthetic mineral based oil and the little gm bottle additive, and Woohoo!!!
We use amsoil in most of our heavily abused car but for the average street stuff it's Royal purple.
Let me know when you are ready and I'll get you worked into the schedule. Clicking while turning could be bad or just the wrong fluid. Should be inspected before it fails.
BTW I was being facetious with the puke usage. : )