Read about it about a month or two ago on goldwingdocs.com, I believe the creator was from that forum also. He designed this for the GW GL1500, not the Valkyrie, for excessive flexing of the shifting stem that causes the oil seal to fail.
I think I recall someone asking if it would fit the Valkyrie, which was maybe yes. But no one there knew if the Valkyrie had the same problem. I don't think so. But I no longer have my Valkyrie to look at to see if there is an issue. I know from here, that the Valk oil seal leaking is not a very common leak, but it is an easy fix.
How-to install
http://goldwingdocs.com/forum/viewtopic.php?f=14&t=19760