The automatic transmissions shift firmly, and owners repeatedly reassure buyers that a hard shift in a video is normal, often exaggerated by flooring the pedal. The vacuum system runs the central locking and modulates shift softness, and a vacuum leak deep in the dash can make automatic climate control default to defrost; the K1 spring kit is a common fix for 2-3 shift flare.
Vacuum system and automatic hard-shift quirks
Mercedes-Benz W123 · mechanical