Transmission

A transmission comprising:

• a fixed transmission part having an internal space defined therein;
• and
• a movable transmission part having an internal space defined therein, the movable transmission part being movably connected to the fixed transmission part via a shaft such that the movable transmission part is pivotally movable relative to the fixed transmission part about an axis of the shaft, the shaft being rotatably mounted to the fixed and movable transmission parts,
• wherein the fixed transmission part has a hollow cylindrical first connecting portion through which the shaft extends, and the movable transmission part has a hollow cylindrical second connecting portion through which the shaft extends, and
• wherein one of the first connecting portion and the second connecting portion is received in the other of the first and second connecting portions with a single seal member disposed between the first and second connecting portions so that the internal space of the fixed transmission part and the internal space of the movable transmission part communicate with each other to thereby form a single hermetically-sealed space for holding therein a lubricating oil.