Transmission Vacumn Modulator
 

I have a 89 300E that has a small leak in the modulator. It appears that the unit is held in place by a couple of bolts. How do I adjust the new unit to shift properly? Is there a vacumn gauge hook up or is it trial by error.

The proper adjustment would have you hook a gauge to the modulator pressure port, remove the vacuum and rev the motor to 2000 rpm.
The pressure attained then would be changed to spec by turning the tee handle in the modulator.

In reality I would suggest adjusting to taste.
It will probably be close where you get it.
Harder = clockwise, softer = counterclockwise.
Do it a half turn a time and if you go more than 2 total turns you probably have a problem.

I've adjusted my modulator, two and a half turn with VERY minimal change, i.e.: 2-3 happens at (on the speedo) at around 48KMh which in reality is probably around 55Kmh (my speedo is out) What kind of problems might exist that would cause this? simply a bad modulator I hope, I have a non leaking vacuum line on a newer (less than 2 years old) cap, O-ring and Handle, attached to an unknown modulator that isn't leaking fluid. No kickdown and the downshift when decellerating is 3rd till 40 2nd till 20. If I gunned it from a dead stop, 2nd gear is hard while 3rd almost wants to runaway. This is all with the throttle rod disconnected at the throttle linkage, because when I connect it and adjust it correctly up top, 4th doesn't happen at all.