You can put the lowering springs for the front on the X, but you need to get lowering links for the rear in order to make the rear air springs sit even compared to the front.

Or perhaps you can lower the rear axle with DIS/GT1 or INPA to match the fronts once the springs are installed?

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2018 Ram 2500 6.7L Cummins 68RFE
19k miles -Bright White/Black - Big Horn Sport - Crew Cab Short Bed
2013 X5 35D (CEO's) - Born on 5/17/2013 -
82k miles - Alpine White/Cinnamon Brown/Premium Pkg, Sport Activity/Premium Pkg and Sound/20" Style 214/Running Boards