I spoke with my contact at Thule and she informed me that yes this Replacement Square-Bar Clamp-On # 853-2156 would work as a replacement adapter for your ski carrier to mount to Thule square bars. view full answer...
I know it's not the news you want to hear, but the only safe recommendation I can make for you would be to find a place you can park your trailer, pull the hubs and get the seals and bearing numbers so we can get you the right parts. I know it's a pain and it leaves you with a trailer stuck on jackstands till you get the right parts but it's the only option.
Hexagonal caps that are threaded are typically used on oil bath hubs.
I would recommend you at least inspect all the components... view full answer...