You can either clean and lube the heck out of it (which is likely to
work - it did for my E28) or get another mast for ~$30 from BavAuto or
your favorite aftermarket supplier of BMW parts.
(Been there; drove that)
having only last year done 2 electric antennae, i can tell you its not
a big job; remove it, strip it out and clean it. once clean you can
see if the teeth on the nylon drive are worn or not.
if they are good, lubricate, re-assemble and test. when re-fitting
make sure you re-connect the water drain. i seem to get a lot of water
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.