I saw that Hirschman now offers a power antenna that's about $100 cheaper than the OE direct replacement. Apparently this newer one might require some modification. The antenna I have now extends smoothly to about 3/4 of full extension, but makes a really loud growling sound when retracting. Should I just take it apart and clean it? Thanks

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'81 300SD

Usually, the problem is the mast and not the antenna mechanism. Replace that first and see if it fixes your problem.