Wpoll, the V8's have ZF trannys and the I6 gassers have GM.

The I6 gassers have the same tranny from introduction to end of production.

The V8's had 5 speeds at introduction, and got 6-speeds during the facelift.

The GM, 5 speed ZF, and 6 speed ZF all used different fluids.

I think the diesels used ZF's as well.

EDIT: yeah, I'm sure you know all that, just trying to frame the scenario in my mind. Did not see the OP post what model X5. Assuming it is an 03 by the user name though.

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04 X5 3.0i auto
03 X5 4.6is