Since you already have the rear diff you want to install, measure to see if bolt holes are in same locations and if the case is the same length from side to side. If there is a difference the flanges from the installed diff are likely longer to make up the difference. I know that the flange is sometimes different but I have no experience with your specific application.

Unless you are doing a lot of highway driving going from a 4.10 ratio to 3.64 might not improve mileage. What will be very noticeable is your vehicle will accelerate slower.

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