(I have been posting on another thread, but it is getting a little long).

Symptoms- moderately hard to neck breaking shifts at all speeds, at all temps, in a 300SDL 87 - 126 with OM603.

I have been monitoring the vacuum line pressure on the line that goes to the transmission modulator and have observed the following:
- idle parked is 14psi
- idle at highway speed (on a big downhill) is "usually" 14psi
- full throttle is around 5 or less psi
- pressure varies proportional to pedal pressure from 14 to +/- 5 psi

All that seems fine. Here is the problem. 50% of the time when on city streets, when I accelerate and get the vacuum below 10psi, the pressure will not return, and often leaks off and hovers around 4psi. I get terrible shifts at this point.

However, if I pump the mightly vac to get the vacuum back to 10psi or so, the needle will usually recover its freedom of motion and will "work like it should" - that is, varying between 14 and 4 psi. The shifts at this point are absolutely perfect.

There are no leaks in my vacuum lines or connectors.

The modulator will hold a 15psi vacuum applied directly to it.

Does it sound like my modulator is toast?

Any help appreciated.

thanks

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84 300TD - 235k - Farbe "Surfblau" bought at 213k
87 300SDL - 131k - Farbe "PimpGold" bought at 115k
00 Klepper Faltboot Expedition Double