I just checked. The mast itself is broken, but when I took it off the base, the male portion of the base was also damaged. The top part of the male piece was only half there and there were only a couple of threads on the bottom that the antenna was hanging on to. By the lack of pieces falling out, I think it's been like that since I bought the truck 10+ years ago. There was also tons of grease packed in there ? ? ? ?

Soooooo, looks like the base is bad, but "good enough". If that mast stayed on for 10+years, I think I can get away with just relacing the mast!