I'm not quite sure why it ruptured, but it did have 170K on it. I kept losing trans fluid and could not find out where it was going. One day I noticed red fluid bubbling up in a vacuum line on the back intake manifold. Sure enough when I tracked the line it went right into the shift Modulator.
The picture was from another great Mercedes Shop forum Member who was patient enough to explain to me where the test pressure ports were on the trans to set the modulator. This was my old post:
Help-Trans fluid in the Shift Modulator vac. tube.
Come to find out most Techs adjust it to feel rather than hooking up a hydraulic tester. They just test drive around; give it a half turn either way to get it shifting right. If it's too soft the gears will almost feel like they slide vs. shifting. And forth will jump way to quickly to fifth.