I just refurbished my dead 6000 antenna, new circuit board, new mast, new seal, wiring was corroded - and yes you need to remove the mast before installling the antenna in the rubber seal on the car. Use battery power to raise the mast and undo the nut.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)