Changing the tranny fluid wasnt a cure all for me either. Def an improvement, but I'm convinced that a clean up of the valve body would be the solution in my case. People have had this replaced ($3000 for the dealer to do) and it has solved their same issues as ours.

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2005 BMW X5 4.4 Sport Upgrades:

Dinan Cold Air Intake
Dinan Stage II Software
Akebono Euro Cermaic Pads
Brembo Rotors
Titan Silver Metal Gauge Rings
DICE IPOD Module
Hardwired Passport 9500ix Radar/Laser Detector