Thanks everyone!
Yes, as I said this is a cheap sulky, although solid, and I do think it is rather old. That being said, it is light, maybe 40lbs, and my mares seem to have no trouble pulling it. However, I am only using it for training this year, so we have mostly been walking, with just a small amount of trotting, on even ground, so I have not seen any adverse effects from the lack of movement such as galling or soreness.
Leia, the singletree on my EE cart was the exact same way! I thought "what is the point of this, it hardly moves". I also took it all apart and oiled and replaced much less tight, and it worked so much better. Now if only my mares would have fit in that cart, we wouldn't be having this conversation!!
Katie