An example downhole apparatus includes a drive shaft with a longitudinal axis, a spherical portion that extends radially from the longitudinal axis, and first and second interfacial surfaces proximate the spherical portion. An outer housing is positioned at least partially around the spherical portion. A radial bearing may be between the spherical portion and the outer housing and coupled to the outer housing. The radial bearing may comprise first and second interfacial surfaces in contact with the respective first and second interfacial surfaces of the drive shaft to transmit or receive torque in corresponding first and second rotational directions. A first axial bearing is coupled to the outer housing and in contact with a first end of the spherical portion to axially secure the drive shaft with respect to the outer housing.