I'm having trouble getting the old modulator off. I'm using a open end wrench but I just can't seem to unscrew it. Am I missing anything or do I just need to use more force.

There is an allen screw holding it in.

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Dave
1983 300D Daily Driver

What year/model would be a good start. Some are held by a metal ring with a small allen-head bolt. (The modulator itself doesn't unscrew.)

Also, what is the reason you are changing the modulator?

I ask this in order to possibly save you a lot of headache and frustration as it isn't just a pull and replace procedure. MB uses the vacuum modulator a little differently than U.S. manufacturers.

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Sam

84 300SD 350K+ miles ( Blue Belle )

It's a '79 300sd (the trans is actually an '80). I though I set my signature line to reflect that but I guess not.
I've owned it for 6 mos and it's always had a bump going from 1-2 and 2-3. The vacuum line was disconnected at the modulator so I reconnected it. It keeps coming off so I'm replacing the vacuum line and the rubber connector (I think all the leaking oil has made it to sponge to hold tightly).
Anyway, I pulled the dust cap off and was filthy inside. My thinking is replace it, start fresh and adjust it properly.
Wolf... is the allen inside the modulator barrel (where the adjustment key goes) or is on the side somewhere like a set key? I looked the new one over and I don't see where the allen screw would be.
Thanks

On my 722.315, there are two allen head srews. One in front of the modulator and one to the rear. These hold a flat U shaped bracket, which holds the modulator in place.

Attached Thumbnails

 

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Dave
1983 300D Daily Driver

Thanks for the photo. That doesn't really look like what I've seen on mine. Is there a nut and threads on the modulator? I'll need to take another look at mine.

On most that I've seen, (not specifically familiar with your year model) the bracket fits over the lip on the modulator and the bracket itself is held with two allen bolts. The modulator is held in place by the clamping bracket.

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Sam

84 300SD 350K+ miles ( Blue Belle )