1990 300SE 2-3 shift flare

[danwatt]

For quite awhile, I've always had a slight flare on the 2-3 upshift. Did some research, but it looks like the k1 piston fix was on the early 80's models. I replaced the fluid and filter (yes, drained torque converter) awhile ago, didn't make much a difference. Fiddling around with the vacuum modulator and bowden cable seems to help a bit, but I feel it's not a quick fix. And I'm pretty damn sure I don't have a vacuum leak. Fluid level is correct. Car just went over the 200k mark. Perhaps it's really time for a rebuild?

And lately, the flare is getting worse. I can jump up 2000 rpm if the pedal is down more than halfway while cold. While the car is hot, the flare isn't quite as bad but it's still jumping 800 rpm or so. WOT upshifts seem to work perfectly fine. Any advice?