Date registered: Jan 2011
Vehicle: 84 300SD (2 ea.), 98 E320 4matic Wagon, 51 Chev 1T pickup, assorted british motorcycles
Location: Seattle, WA
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Having been through this set of problems I might be able to help. First, I think you are mistaking one problem for another. The K1 and 2 spring thing will cure the 2-3 shift flare and supposedly the harsh 1-2 shift, although in my case it didn't fix the 1-2- shift. So, that was a good thing to do; you probably didn't waste your time.
You still have harsh shifts, though. This probably relates to engine tuning as the throttle position, not engine load determines oil pressure at the time of a shift. As has been discussed time and again. Diesels have no manifold vacuum and turbos have pressure. So MB had to create synthetic vacuum to control the 722.3xx transmission that was used on the gassers and diesels. Aside from base case-pressure that affects all shifts, throttle position alone determines how hard it shifts at part throttle. If it shifts hard on wide open throttle then the case pressure may be too high.
So, if all part-throttle shifts are hard, that indicates that the engine is putting out less power than it did when the vacuum control was last adjusted. Low power has a raft of possible reasons: clogged fuel filters (there are 3), dirty injectors, low compression, poor fuel quality, incorrect injection timing, heavy engine load from A/C, high altitude for which the ALDA has not compensated, low turbo boost and the list goes on.
I would chase down engine performance issues first. If you want, you might replace the B-2 piston as a preventative measure. Buy the piston which comes with a bushing and a seal as I remember. You need to replace them both according to the instructions that come in the box.