1988 MB 300E, Auto, 114k. I just purchased the car but it has a strange transmission problem. It does not slip, it just shifts high, and does not like to down shift. Starting out driving from a stop, not pushing it hard, it will rev to around 3500 rpm or more sit there for a second or two or three then shift, sometimes up one gear, sometimes up two. The actual transmission seems fine, just seems like the shifting points are out of wack, I've read about the vacuum valve on the modulator valve? Also when giving it good amount of gas it doesn't like to down shift, sometimes it will, other times it will downshift and catch at about 5500 RPM's. Any ideas before I take it in? BTW the fluid looks new, but I'll change it with filter anyways this week.

 

The modulator only adjusts the firmness of the shifts. The shift point is determined by the bowden cable. I would lengthen it a bit. I can't tell you which direction to turn it, but you want the throttle to pull the cable less. As far as the down shift, there is an electric switch under the accelerator pedal that it activates when you floor it. You have to apply around 15 pounds or so of pressure to the pedal to activate it. I drove mine for several months before I discovered it. It feels like you are going to break the pedal because of the amount of force it takes.

 

LOL on my 124 with the tiny little engine, I use it a lot and now the switch takes minimal effort to activate! Use it more!!