Diff leaking around the bolts

[Synchro909]

Originally Posted by denniskliesen

I prefer Permatex High Tack gasket sealant over #2. You can buy it in spray or brush on. I've used it on my differential housings, transmission, and over 6k miles no leaks. I also used Ultra Black under the head of the bolt and medium strength on the threads.

What is Ultra Black???? Probably like that Indian Head stuff at $70 a tube by the time it gets here. Does Permatex Higfh Tack work on oily threads or must the surfaces be squeaky clean?
It's nearly 9am here and I'm about to leave to check out what is available while bearing in mind what I has been suggested here.