I am finally revisiting my '82 300D-T's vacuum system as it pertains to the trans control. A few months ago i replaced the switchover valves hoping to fix my trans' hard-shift-all-the-time problem. These are the white vacuum valves located on the valve cover under a black plastic cover. The old ones not only had the plastic finger worn off but the valves themselves were no longer porting correctly. They influence (with vacuum) the trans modulator, the EGR and the injection pump. I replaced them with a brand called MTC (not genuine MB). They look the same, have the same part # and worked OK upon receipt (port 5 and 2 open at idle and port 5 and 3 open at partial to full throttle. I guess they work by providing vacuum to the trans modulator at low throttle (soft shift) and no vacuum to the modulator at partial throttle (hard shift).

In any case after just a few months the switchover valve no longer ports vacuum correctly, 5 is open to both 2 and 3 at vacuum. The genuine MB switchover valves are double the price at about $40 compared to MTCs $20. Anyone else had experience with faulty switchover valves by MTC? I hate paying for these again especially at $40!

I already avoid using non genuine trans pan gaskets and frame/subframe bushings (I also confess to only using MB coolant on my MBs). Are MTC switchover valves another one to avoid?

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1972 450SL
1982 300D Turbo