I've been struggling with this since I got 2013 installed, and I can't figure it out. Why can't I rename parts in assemblies? I used to be able to open a part from an assembly, save it as a different name, and when I went back to the assembly the name was changed. I can't do that now. The new name will save, but the assembly retains the old part name. If I try to replace the part with the newly named part, SW says I can't replace a parts with the same name, yet the names are clearly different. I can't RMB on the part and find "rename" in the menu, and I can't double click in the assembly feature tree to rename it. Searching the Interent was no help either.