I bought a new (to me) 81 300td. and i have a bad leak in the shut off system, which i had little power assist in the brakes, so i blocked it off temporarily. but my question is when i hook the vacuum line that gos to the transmission straight to the nob on the thick vacuum line (from the brake booster to vacuum pump) my car shifts like butter i don't feel the shifts at all. but when i hook it up according to the diagram with the three way rubber hooking up the vacuum control valve and surge damper to the automatic transmission line the car runs quieter but shifts harder, and i think it may be leaking since after a while i don't have power assist brakes. so i was wondering if the vacuum control valve and surge damper is really needed?

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1974 240d
1983 240d -sold
1989 420sel with om606
1994 s350 turbodiesel - sold