Originally Posted by Jeremy5848

I have a similar problem with my 1987 W124 300D-T transmission (722.357 is the number on the transmission although EPC says it should be a 722.317). If one is very light on the throttle, the transmission shifts nicely but at low engine speeds. If the footfeed is pressed down farther, the transmission stays in whatever gear it is in longer, allowing the engine to wind up above 4000 RPM, but then shifts with a jerk. Warm or cold (machine and/or environment) does not affect this much, if at all. Downshifts are not harsh.

My 1985 W123 300D California version has a similar transmission (722.416) and the '96 210 has a 722.438. Both shift normally, giving me a little idea of what the 124 should be like, more or less.

I tested the modulator according to Brian's suggestion, removing the vacuum line to the transmission after the green damper. After pumping the Mityvac to 18" Hg, I allowed it to sit for 18 minutes, by which time the vacuum had dropped to 12" Hg and I got tired of waiting so I disconnected.

This would seem to indicate that the modulator is OK, not leaking, and the problem is elsewhere. I have not adjusted the Bowden cable at all -- from my understanding, it affects only the RPM at which the transmission shifts, right?

I plan to go through the vacuum system and check all of the components, then run a line into the passenger compartment and watch the vacuum at the modulator line while driving the car. I understand that the vacuum is supposed to be lower with more throttle, mimicking the way a gasser engine works.

Anything else I should check?

Jeremy