Hmmm, I did fluids for both and IIRC the older pre-facelifts use ATF, Dexron 3, and the Xdrives use a special fluid.

I'd go OE or equivalent, and there was no equivalent for the Xdrive fluid at the time so I went OE.

It was expensive but it's only a quart and not often.

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04 X5 3.0i auto
03 X5 4.6is