According to the repair/service manual I have for the MB doors, a "viscous moly grease" is used for the check straps, and they only mention "grease" on the gear teeth. The bottom and vertical track it just said "lube" them. I used syn grease on the teeth, sunroof slide grease on the two tracks and a product called waxlit on the fabric/rubber that the glass slides through at the bottom of the window opening. After running the window up and down several times it is now the smoothest operating of the four. Three more to go. While doing that, I pulled the electrical connectors and applied dielectric grease. Hope this helps.
Steve

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Steve
'87 300TD - 132K - Soon 4-Sale
'84 300D Turbo - 122K - Driving
'77 VW Type II - 77K - Restored
'08 250EX Ninja
English Bulldog (Brier) - My best friend. Passed away 12/02/04 while in my arms.