A skilled welder/machinist could either shorten or lengthen the tube behind the ball to move the seal contact area to an unworn area of the torque tube. It would require a huge lathe with long bed ways and a center rest to spin the entire torque tube and carrier housing to smooth up a weld repair of the groove itself, and probably a tool post grinder to get an acceptable finish at the repair. That kind of work would probably cost considerably more than locating a replacement torque tube. Modifying the ball section would be a lot more practical, and less expensive.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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