I'm a little late with this reply, but just saw this series for the first time. As I remember all those old boxes leaked something awful. I an working on a big truck and was going to put grease instead of oil in the box. I found a reference to Penrite Oil Products somewhere on this site, and then contacted Classic Auto Lubes at WWW.Classicautolubes.com. He recommended an oil they have made specifically for gear boxes, which he claims to have excellent results with. According to the dealer, it is an oil, but will not leak. I ordered enough to fill my steering box. I hope it works. Will let you know later. Allen