Abstract: A mainshaft assembly for a gearbox includes a mainshaft (44) and drive gears (31, 36) carried for rotation about the mainshaft. First and second hubs (50, 50?) are associated with respective drive gears, each hub being operable to selectively couple or uncouple with the drive gear causing it to rotate with the hub or with respect to the hub. A drive connection mechanism (42, 64, 66) associated with each hub selectively connects the hub to the mainshaft. Upon connection of the hubs to the drive gears, the drive connection operates to connect one or other of the hubs to the mainshaft when torque is applied to the mainshaft in a first direction or an opposite direction. This enables a gear ratio to be selected by reversing the torque being handled by the gearbox.

Abstract: A mainshaft assembly for a gearbox and a gearbox embodying such a mainshaft assembly are disclosed. The mainshaft assembly comprises a mainshaft (44), and several drive gears (31 . . . 36), each carried for rotation about the mainshaft, each drive gear having a different number of teeth. The assembly includes first and a second hub (50, 50?), each being associated with a respective drive gear, each hub having a dog ring (54, 54?) operable to selectively couple with the drive gear causing it to rotate with the hub or uncouple from the drive gear to allow the drive gear to rotate with respect to the hub. A respective drive connection including a cage (42) and pawls (64, 66) is associated with each hub and selectively connects the hub to the mainshaft for rotation with it or to allow rotation with respect to it when the pawls are displaced against a spring bias.