Shockproof comes in a 80W90, if I remember correctly. There are microscopic buffers to prevent metal to metal contact. It says nowhere that the viscocity is a 75W250. In fact, it says on their website that it protects better than a 75W250 would.
It's red and thick and smells like ****, but I had it in my Mustang's 8.8" fully built rear end.