SkiFreak
Crazy Person
Quite simply, it is called a key and that fits into a keyway.
This system is very common on driveshafts, but it relies on a snug fit between the two parts in order for it to function correctly.
As you have eluded to, the keyway is pretty flogged out, so simply getting a new key is unlikely to resolve the problem, as it is unlikely to fit correctly. The two parts should be a very neat slide fit, with minimal or no play.
Keys are normally standard sizes and you can buy key steel to make your own, if that is something you have the capacity to do. I have made many over the years.
However... I also expect that the corresponding keyway in gearbox would likely be damaged too, which complicates matters.
To fix this problem properly you would need to replace all of the worn/damaged parts.
This system is very common on driveshafts, but it relies on a snug fit between the two parts in order for it to function correctly.
As you have eluded to, the keyway is pretty flogged out, so simply getting a new key is unlikely to resolve the problem, as it is unlikely to fit correctly. The two parts should be a very neat slide fit, with minimal or no play.
Keys are normally standard sizes and you can buy key steel to make your own, if that is something you have the capacity to do. I have made many over the years.
However... I also expect that the corresponding keyway in gearbox would likely be damaged too, which complicates matters.
To fix this problem properly you would need to replace all of the worn/damaged parts.