JHPSTANG

I want to top off the rear end before going for first drive tomorrow. When building rear brakes I moved one hub and felt some play and a clank before the diff moved the other wheel (I think). Sounds like the rear end might be low on oil?? So what gear oil should I put in? I've read that Royal Purple 75-90 is good, but I'm not changing, just topping off for now so probably want to stick with non-synthetic. I don't know what's in there. Any advice?

RolandT3Speed

Any API GL4-5 hypoid gear oil should be fine. I use 85/140. It's hot here.