The old gear lube probably has turned to a thick semi fluid through the years, but originally it was gear lube, probably 90w. If gear lube leaks out, something like stp would probably help. I had one leaking real bad that I took the cover off and cleaned it with a pressure washer and then filled it with semi fluid synthetic grease such as Mobil lith 007. We run this in our trailer wheel bearings and usually forget about it for 1/2 million miles. Synthetic does not mix with petroleum based lubricants and you must re adjust your sector if you remove the cover. It probably needs adjustment any way. I take the drag link off, tighten it to where you can just feel a little drag when you turn the steering wheel with one finger. Be sure that you try it from stop to stop. There is probably a worn spot in the middle and if you tighten it too much it will not return on its own when you turn. Not scientific, but it worked for many years.
