If the solenoids go faulty (all too common with the 6HP26) then there’s a high likelihood that the corresponding damper (each proportional pressure control solenoid has its own separate accumulator/damper in its hydraulic clutch circuit) has become worn and ineffective as a result. The damper is made up of a solid metal piston into which is embedded a rubber ‘spring’. The rubber spring flattens over a period of time, becoming permanently deformed.

https://i260.photobucket.com/albums/...psgr1tgdlo.jpg

The accumulators/dampers should therefore be replaced when the solenoids are changed. The Sonnax zip kit replaces this damper design with a cupped metal piston with a traditional wire helical compression spring.

https://i260.photobucket.com/albums/...ps7fb6eb41.jpg

Phil

SO I too just had my ZF6HP26 valve body (separator plate B052) replaced by a new unit from RevMaxconverters.com and it too has made my tranny new. I have owned this x5 for 10 years now and It's never shifted this smoothly. I barely notice it moving about honestly. SO GLAD I went this route.
Perhaps the upgraded aluminum, instead of plastic bits, will help but I don't care as long as it lasts. Expensive but built properly and has 1 year warranty as opposed to me buying the ZF kit and repairing and if I had screwed up something badly, I could be back to square one repairing again. Buying this and returning my core (free, since they include a UPS core return sticker) was smarter and got my x5 back on road faster.

Glad to hear! Mine is chugging along too.

The Revmax option is the best remanufactured value out there (BMW remanufactured is over 2K) compared to rebuilding the transmission valve body on your own. Just the parts alone are $400 + (solenoids, gasket and sonnax zip kit) and the cleaning of the valve body and machining of the mating surfaces based on the process described on their site seems to beyond a DIY project. The Sonnax zip kit seems to address a lot of the inherent issues with some of the internals. Most of the internal rubber seals are in need of replacement by now anyhow.