No, it's a gearshift hand lever ("stick") that actually ends in a real eight-ball from the game of pool, wherein balls with various numerals are struck by a stick on a table. The goal of the game is to hit all the balls into holes, or "pockets," on the sides of the table. The last ball must be the 8-ball. If you accidentally hit the 8-ball into a pocket prematurely (before all the other balls have disappeared), you lose the game. So a person who is generally a "loser" in life is said to be "behind the eight-ball."
So the hand of the driver grasps an actual eight-ball, instead of an ordinary knob, at the end of his transmission lever. A driver who installs an eight-ball on the lever implies an ironic view of himself, as being "behind the eight-ball."
