It's the pivot on the part that mates to the centerlink. I will try to post pics on it this evening. The part is so loose inside the idler arm you can move it around like it's a ball and socket.
It is a ball in a socket. Same as a tierod end. It has a designed amount of movement but to exceed that will blow out the top of the socket.
If modern technology has incorerperated a synthetic/nylon insert inside the heat may be destroying it. In that case there may not even be a grease fitting. That's how they tend to make things today.
Could explain why most 40 year old idler arms are still in good condition at the ball-socket end and worn out at the bushing end. Just guessing.
