The "rear yoke"- - - -"companion flange" etc. is the part where the rear universal joint attaches to the center section of the rear end. Is that part missing? Why do you need to replace it, if it's still there? It's held on by a single, VERY TIGHT nut and flat washer. New yokes are probably not available, since that rear end was discontinued sometime in the late 1950s or early 1960s. A "speedy sleeve" is a thin repair sleeve that is pressed over the seal surface of a yoke to cover a groove worn into it. You would need to measure the diameter of the seal surface and consult a bearing supply company catalog such as Timken, SKB, Bower, etc. to get the right size. Repeated leak problems there are usually caused by one or both of the pinion bearings deteriorating, that allows the pinion shaft to wobble and cause the seal to fail.
Jerry
