Inline six drive shaft

[1978allison]

I have an old inline six drive shaft (1978) that has some wear(grooves) above the water pump key slot about 1 inch overall height. This is something that I am not familiar with. Is this reparable? What caused the problem?

[Dave S]

If the stainless insert had spun at one time it may have caused this. If not too deep n/p.