A washing machine appliance may include a tub, a basket, an impeller base, and an extended post. The impeller base may include one or impeller fins and a mounting face. The mounting face may include a threaded bracket defining a mounting thread extending about a rotation axis. The mounting face may define a vertical slot radially inward from the mounting thread. The extended post may be removably attached to the impeller base to rotate therewith. The extended post may include a base body, an auger fin, and a mating face. The base body may extend between a bottom end and a top end. The auger fin may extend radially from the base body. The mating face may be disposed on the bottom end. The mating face may define a mating thread matched to the mounting thread to rotatably enmesh therewith.