This is the speedo drive for the Cavalcade. It is easily disassembled so that it can be greased. This should be done each time the front tire is replaced. By doing so, the drive can last indefinitely.
In fact, I would do this to a brand new drive as the factory does not put enough grease in them.
The drive is held together with a wire snap ring. It can be removed with a thin-tipped screwdriver (like a jewelers).
Once the ring is released, follow it around the housing with the screwdriver.
CAREFUL! Keep your hand on it so it doesn't fly across the room and get lost.