A washing machine appliance may include a tub, a basket, an impeller base, and an extended post. The basket may be rotatably positioned within the tub. The impeller base may include a mounting face including a threaded bracket defining a mounting thread extending about a rotation axis. The extended post may be removably attached to the impeller base to rotate therewith. The extended post may include a base body extending along the rotation axis between a bottom end proximal to the impeller base and a top end distal to the impeller base. The extended post may also include auger fin extending radially from the base body between the bottom end and the top end. 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.