Crumbling wire sheathing

[flyguy]

I have been replacing the receptacles and switches in a condo circa 1947. There is both aluminum and copper wiring. The aluminum sheathing seems to be woven but the last receptacle is copper with a plastic sheathing that is crumbling. The box is metal and there is only about 3 inches of wire to work with. As far as I can tell, there is no way to pull new wire to the box (brick external wall of a condo), so I'll need to pigtail some romex inside I guess. Is there a better approach? Anything I can do to maintain the integrity of the original sheathing?

[HayZee518]

wire insulation around that date is a woven jute fiber around rubber. over time the rubber hardens and flakes off if its messed with. about the only way you can save it is to use a shrink tubing over the jute fiber. you don't necessarily have to shrink the tubing just get it on all the way. any flexing is sure to crack the original insulation but the plastic will keep its insulation properties. aluminum wiring requires special knowledge of how to splice and maintain.