[Henk]

The Automatic Gearbox on my 1982 280E has a harsh shift from 1st to 2nd, and a somewhat harsh shift from 2nd to 3rd. I've seen some articles that describe adjusting the vacuum modulator to adjust shift quality on diesel MB's. Does the same apply to the gas models? I've had a look at the gearbox, but could not identify where the modulator is located. Do I have one, and if so: where exactly is it located and how do I adjust?[?]

 

[dfwdiesel]

On early 123's the modulator is on the passenger side of the trans, on later it can be on ...

On early 123's the modulator is on the passenger side of the trans, on later it can be on the driver side.
The clue is you will see a vacuum line coming out of it. You pop a cap off to get as a T Handle that turns.
I can't remember which way goes harder and which way goes softer.

In any event adjusting the modulator is the last thing to do in a series. First change the fluid and filter. If it looks burnt or really dirty. Drive awhile and do it again. Sometimes even days to break more dirt loose. Fresh fluid can clog a new filter
in a dirty trans. Also look for vacuum leaks. Look for other vacuum problems.

Then lastly look into adjusting the modulator.
Changing it too is not a bad idea, about $40 for the part.

I changed a 123 trans and the modulator gave me fits until replaced it. Mine had been slightly bent when the transmission was out. Only caught on after I pulled it out and compared it with a different one.
John Gregg