A pulley assembly for mounting on a rotatable shaft of an agricultural harvester, the pulley assembly being configured to be operable in a high-speed configuration or a low-speed configuration, the pulley assembly comprising: a high-speed pulley having a high-speed running surface for receiving a drive belt when the pulley assembly is in the high-speed configuration, a mount for mounting the high-speed pulley to the rotatable shaft for rotation of the high-speed pulley about a central axis, and a storage surface; a low-speed pulley having a low-speed running surface for receiving a drive belt when the pulley assembly is in the low-speed configuration, and a mounting surface for mounting the low-speed pulley to the high-speed pulley; and three sets of teeth (68, 50, 52), each set of teeth (68, 50, 52) comprising at least one tooth that extends either from the mounting surface radially towards the central axis or from the storage surface radially away from the central axis, and wherein a first set of the three sets of teeth extends from a different surface than a second set of teeth and a third set of teeth of the three sets of teeth, wherein: in the low-speed configuration, the running surfaces (36, 62) of the low-speed pulley and high-speed pulley are axially aligned about the central axis and the first set of teeth and the second set of teeth are engaged; in the high-speed configuration, the running surface of the high-speed pulley is exposed for receiving the drive belt, the low-speed pulley is positioned beside the running surface of the high-speed pulley along the central axis, and the first set of teeth and the third set of teeth are engaged; and the pulley assembly being configurable between the high- and low-speed configurations by disengagement of the teeth, movement of the low-speed pulley along the central axis, and engagement of the teeth. a high-speed pulley having a high-speed running surface for receiving a drive belt when the pulley assembly is in the high-speed configuration, a mount for mounting the high-speed pulley to the rotatable shaft for rotation of the high-speed pulley about a central axis, and a storage surface; a low-speed pulley having a low-speed running surface for receiving a drive belt when the pulley assembly is in the low-speed configuration, and a mounting surface for mounting the low-speed pulley to the high-speed pulley; and three sets of teeth (68, 50, 52), each set of teeth (68, 50, 52) comprising at least one tooth that extends either from the mounting surface radially towards the central axis or from the storage surface radially away from the central axis, and wherein a first set of the three sets of teeth extends from a different surface than a second set of teeth and a third set of teeth of the three sets of teeth, wherein: in the low-speed configuration, the running surfaces (36, 62) of the low-speed pulley and high-speed pulley are axially aligned about the central axis and the first set of teeth and the second set of teeth are engaged; in the high-speed configuration, the running surface of the high-speed pulley is exposed for receiving the drive belt, the low-speed pulley is positioned beside the running surface of the high-speed pulley along the central axis, and the first set of teeth and the third set of teeth are engaged; and the pulley assembly being configurable between the high- and low-speed configurations by disengagement of the teeth, movement of the low-speed pulley along the central axis, and engagement of the teeth. in the low-speed configuration, the running surfaces (36, 62) of the low-speed pulley and high-speed pulley are axially aligned about the central axis and the first set of teeth and the second set of teeth are engaged; in the high-speed configuration, the running surface of the high-speed pulley is exposed for receiving the drive belt, the low-speed pulley is positioned beside the running surface of the high-speed pulley along the central axis, and the first set of teeth and the third set of teeth are engaged; and the pulley assembly being configurable between the high- and low-speed configurations by disengagement of the teeth, movement of the low-speed pulley along the central axis, and engagement of the teeth.