1966 Driveshaft - Which End is Front?
That is the wrong needle adapter. It is a hypodermic type used for greasing sealed bearings and things not meant to be serviced or greased by poking the needle into or under the seal.
The flush mounted grease fitting you mention requires a needle like this to grease.
http://www.oreillyauto.com/site/c/d...se+gun+needle_-1_-1&keyword=grease+gun+needle
That little fitting in your cap has a spring loaded ball that you use this to inject grease through. You should be able to buy one at any industrial or automotive store
One more thing about these u-joints. They have a single flush mount grease fitting installed in one of the caps. Call me a newbie, but I've never seen a flush mount grease fitting before. Had to do some googling to learn what that's all about. I guess I need a needle adapter, like this, to grease them. Tried replacing them with a standard zerk fitting, but the threads are smaller.
That is the wrong needle adapter. It is a hypodermic type used for greasing sealed bearings and things not meant to be serviced or greased by poking the needle into or under the seal.
The flush mounted grease fitting you mention requires a needle like this to grease.
http://www.oreillyauto.com/site/c/d...se+gun+needle_-1_-1&keyword=grease+gun+needle
That little fitting in your cap has a spring loaded ball that you use this to inject grease through. You should be able to buy one at any industrial or automotive store