Abstract: A rear-tine roto-tiller with a chassis having a forward end and a rearward end; a set of rotating tines at the rearward end; a set of ground-engaging wheels between the forward end and the tines; and a tine transmission mounted on a substantially vertical shaft at the rearward end with a substantially horizontal shaft holding the tines. The tine transmission is rotatable about the vertical shaft between a first position in which the tines rotate in the same direction as the wheels and a second position in which the tines rotate in a direction opposite the direction of rotation of the wheels, thus allowing easy conversion between SRT mode and CRT mode.