Had my mercedes tech friend install this the other weekend (as per the CEL code) because the tranny would 'shutter' at high speed (dead stop to entering the highway) and have a problem automatic shifting/downshifting itself.

After the install it seems to be worse; it revs waaaay high (4.5-5k) and finally kicks into gear. It doesn't 'seem' to be slipping because it has the power to match those high revs.
Can that vacuum modulator be adjusted at all?

 

Yes, it has a hat on it. Take that off there is a metal T inside. Pull it out just a little and twist clockwise for more pressure. Start with one full turn, then build from there. A little is a lot.

Never heard of modulator throwing a CEL. The problem you are describing is a called a flare, it usually indicates that your clutches are wore out. Might be time for a rebuild. Did you check your trans fluid? Is it really brown and burnt?

-Michael

 

The vacuum leak threw the CEL; all the hoses checked out fine. Going to have him do a tranny flush, replace all gaskets (there is a leak) and adjust the modulator this saturday and hope that takes care of it ::fingers crossed::

If it's the tranny, then I can't afford it although my tech friend (who does all my work for free!! bless him!) mentioned that there are aftermarket trannies that are better and cheaper than OEM. He also mentioned a 'flex disc'?