Tref,

The drive "clutch" is adjustable, bend the lockplate tab away from the large nut and turn the nut clockwise for more tension and counter clockwise for less tension, I would not deviate to much from its original adjustment (no more than +/- a nut flat or two).When I bought my 83 300SD the antenna did not operate, besides the kinked mast, the ratchet gear that controls the limit switch had a couple of broken teeth, I replaced that gear, then found the worm gear wheel that the motor worm drive mechanism engages was stripped, which was originally caused by the kinked mast and the "clutch" assembly not slipping enough to keep the drive componets from being damaged.I replaced the worm gear wheel and now have a completely functioning factory power antenna. The antenna in my car is the Hirschmann Auta 6000u.