Error codes can be deceiving. Specific symptoms can be associated with more than one cause. I suggest going to a well recommended transmission repair shop that routinely works on BMWs.

A symptom that identifies the the torque convertor as the core cause is that often there is a whine at idle. In park less, and increases in drive

The 4.6 has a beefier torque convertor.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas