It's a Permatex product. There are stronger RTVs, but I like it for diff covers.
The greys would be the next step up if you wanted something stronger. They are harder to clean off though. So if you plan to pull it again, you might not want grey RTV. If you plan to install something like the Ford cover with a drain and don't plan to pull the cover again, maybe the stronger grey stuff would work.
I always let any RTV setup for as long as reasonably possible before putting water or oil back in. I also put a thin coating on both sides of a gasket, if I have a gasket. Just rub it in enough to saturate it.
I also use pipe dope, teflon tape, then more pipe dope on top of the tape on any threaded fittings in my house and pool.
I don't have leaks.