Harsh Shifting- out of ideas. Help!
 

I am at my wit's end.
The patient is a 1993 190E 2.6 with 138k. Transmission is 722.409. When I got the car, it had a little jerk going from 2-3, and the problem swiftly deteriorated into a slight jilt 1-2, a harsh clunk from 2-3, and a jerk from 3-4.

So far, I have replaced the filter with an Elring-Klinger, MB- spec Titan ATF, K1 spring accumulator valve, and even cursing it out in German. Tonight I replaced the vacuum modulator valve, and tuned the pressure exactly to the specified 48 psi/ 3.3 bar.

This seems to have angered Karl Benz even further, as now the jerk from 2-3 will knock the wind out of you unless you are very authoritative with the throttle.

The author of the guide on replacing and adjusting the vacuum box, "Hattenator", advises not to adjust the vacuum pressure by feel, but at this point anything that improves the problem is fair game. Please advise!

Have you inspected the drive shaft flex disks? It's a common problem and makes it feel like yoir transmission is fed up. The fact that staying on throttle smooths it out is what makes me think of this. Less time for backlash when you are hard on the pedal.

Thanks for your reply, Ævarex. Yes. The front flex disc was pretty ratty, as was the trans mount. Replacing them fixed some sloppiness when first selecting D, R, or P.

Meanwhile, I've adjusted the nut on the transmission bowden cable, which has gotten the trans to shift around 2500 instead of 4200, which puts me back where I started at least - it's drivable. The shift quality is still rough, which tempts me to lower the vac modulator setting ad-hoc a little. Meanwhile, I'm still open to other tips and pointers.