On 81-85SDs and other vehicles there are slides that go in the various tracks on the window frame.

If you have access to cars in a yard, you may just want to swap in a regulator with motor. Again, on later models anything from a 126 will work as lond as the motor and window regulator are taken as a unit.

scroll down to sliding jaw and bushing to see what I'm referring to on the 126.

1984 Mercedes-Benz 300SD Base Sedan - Panels & Doors - Page 1

here's something for the 116 (see window regulator kit.
Pelican Parts - European Automotive Parts and Accessories - Porsche • BMW • Mercedes • Volkswagen • Audi • Saab • Volvo • MINI

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.