i got a 1990 500sl for free (it wasn't cared for at all) and on the ride home, i noticed that every time the car would shift, it would do so very roughly and from what i can remember, kind of loud too. ps. the car has 138K miles and i have no clue what the service history was like. ie. fluid changes or tune ups, but i can tell by the condition of the rest of the car that the weren't peformed regularly.

Vacuum control for shift quality. IF the vacuum line to the engine is disconnected, the trans will shift HARD.

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