I was having issues with an assembly not cooperating in the usual way when I realized it was created with an outdated default template.
I did some searching and found several posts that stated it was not possible to update a template once the assembly was created.
What I did.
I opened the assembly, and a new assembly from the template I wanted.
I then added a component to my blank assembly, selecting the existing assembly.
To recreate my explode I selected the entire assembly and created a new exploded configuration by checking the REUSE SUB ASSEMBLY EXPLODE.
If you do not have an explode you can right click the sub-assembly and select dissolve sub-assembly.
Hope this helps someone.