The actual armor is classified.

It’s not like just taking out some computers or electronics or something. The armor on an Abrams is not one solid sheet of metal, it’s multiple layers of materials, including DU and ceramics. The composition of the armor package on the Abrams is classified and not something we share, not even with our closest Allies like the British, Canadians, or Australians. So they need to be re-built to remove the classified armor components and re-fitted with an unclass alternative.

It’s is a major overhaul.