My 190E (107K miles) is shifting pretty hard between all gears. I had a leak fixed at the cap on the valve, and the shifting improved 100% after that, but after about 4 weeks, it has started to shift abrubtly again for about 5 minutes after the car is driven. After this, it shifts smoothly. I think I've got vacumn to the modulator, and now I need to understand the valve a little better. So, a couple of questions. How is it adjusted? What is the best way to access it? If you could explain briefly how the valve works and what you change with the adjustment it would help me with the troubleshooting. My documentation doesn't describe it at all. I know that leaking vacumn connections probably account for most of the problems with the proper operation of this valve, but what is the failure rate of the valve itself, and is the failure mode different from a leak in the vacumn line or fittings? If it's not the valve, any thoughts on the next step?

The valve can leak internally and can be somewhat intermittant in nature (IE sticky) and when warm act differently than when cold. The way to adjust it is to pull off the little cap on the front of it and slide the key ou to the top of it very slightly. Turn in at 90 degree increments to firm the shifts and out or counterclockwise to soften.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM