Abstract: A plunging constant velocity ratio universal joint with inner and outer joint members having opposed pairs of straight grooves receiving balls for torque transmission, and a ball cage with inner and outer part-spherical surfaces, wherein the inner part-spherical surface of the cage engages a number of elements constrained to sliding movement along the lands between the grooves in the inner joint member. Each element may have a projection engaging in a groove in its land, and may be able to rotate about such projection. Frictional resistance to plunge of the joint is minimized by ensuring that the balls roll rather than skid along the grooves in the joint members.