50 chevy 3100,

This is a question that comes up every so often. The original lube is not available. A product called Penrite Steering Box Lube is an excellent replacement (but is not widely available).

Everyone seems to have their own opinion on what to use and why.

I use chassis grease (I think the original steering box lube was equivalnet to 1200 weight oil/grease).

To see more opinions. Use the "search" feature above. search on the string "steering box" in all open forums. This will give you a few discussions on this topic.

Good luck,
Tim