My steering box leaks badly and needs the seals and gaskets changed. However, I have it from an old mechanic that worked on these trucks at a Chevy dealership that the best thing to use is STP oil treatment or "engine honey". He says its is viscous enough to be effective and due to its purpose, reduces or elimenates leaks. It has helped. The only downside is that when it does leak it stinks something awful when it gets on the engine block.
