The seal on my antenna is dry rotted, and I want to replace it with a new seal. Here is what I could get atparts4vws.com I dont see how I could slip the new seal over the black "nub" of the antenna. It seems as if I would have to unscrew the whole assembly, and put the seal down, then screw the "nub" on top. Has anyone done this? Can anyone help me out? Thanks.