Universal Joint

It's simple enough with a couple of sockets and a large bench vise. First, remove the keeper rings that should be just inside the outside of the yoke and against the caps of the U-joint. Use a socket that's a little smaller than the hole on one end and one that's larger than the U-joint cap, on the other end. Put the whole thing in a bench vise and start clamping. The vise will push the smaller socket into the hole in the yoke while the larger socket provides a hole for the cap to go while the socket presses on the edge of the yoke. Once the caps are pushed through, you can remove the cross piece and press in the new joint.

HINT: Once the new joint is in place, hold the shaft up and give it a good tap with a ball-peen hammer. The vibration will "set" the joint and loosen it up. It should swing freely.