2005 4.8is transmission shifting / slipping issue

[RRPhil]

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.



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.



Phil

[Clockwork]

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.

[amancuso]

Originally Posted by Clockwork

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.

[gregy]

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.