Mystery grease fitting problem

[Kube]

Originally Posted by TomC750

My '41 Mercury was missing the grease fittings on both the front and rear springs. They are of an odd thread size. I bought new ones from Third Gen Auto. They included new extender nuts which I did not need as the old ones were present. Now comes the problem - Because the extender nuts (both old and new) have slots on the threaded id, the grease extrudes through this path as I would expect it to do being that there is no way the grease fitting will seal against the extender nut. What am I missing here?

The fitting has a tapered thread; thus, you are not missing anything. If the fitting is proper and was not cross threaded, the should be no leakage.
By the way, grease is not used in this place. You won't be able to find proper lubricant anymore. When I had finally used up my bucket (OEM) of leaf spring lubricant, I switched over to STP oil treatment.