carrying into an open truck on Shabbat

Shalom Rav, I have a situation where over shabbat I am in a place with no eiruv. however the building has several openings for trucks to park, meaning the truck backs directly to an opening in the building made to fit that truck. is there an issue to take stuff from the truck or carry onto it on Shabbat? what if there is only an opening made to take stuff off it (such as to unload water) bit not big enough to walk through, is the truck now considered part of the building? thanks!

It is not part of the building but it is considered a private domain and to carry from one private domain to another, as long as they dont belong to two different people, then it is ok.