Today I had all my fluids replaced. I have a '06 XK limited 5.7L with 67K. I just bought it 5 months ago. Recently my diffs started chattering when doing slow sharp turns. I figured I might as well have ALL my fluids changed. Front/rear diffs, transfer case, transmission, engine oil, and coolant. (and related filters) it cost $350 in fluids/filters and another $150 for labor. Turns out, some moron put ATF fluid in the front diff, which is odd as the car fax showed a lot of maintenance being done by the previous owner at the same dealership they bought it from. You would expect them to use the correct fluid. But anyways, all good now