A great fix: (and one I've used often over the years), for your broken nyloncabled O.E.M. GM broken Antenna Mast. I integrate the use a "metalbraided" mast cable. I've used this method many times, and for ME it works !. I had some garagedoor cables laying around: and I thought: Hey: "that my work" ... and I've done it ever since. IF your old mast isn't kinked / bent, just remove the old nylon crimpedin cable, burn the ole nylon out; and simply SOLDERIN a nice METAL Cable.

This dismisses powerantenna issues PERMANENTLY for me / DONE. Have a look.