One problem related to differential unit has been reported for the 2004 BMW X5. The most recently reported issues are listed below.
1. Did a 3 point turn and then pulled onto a 45 mph road way 2. Front tires locked up and I skidded to a stop, even after I depressed the clutch. 3. Front differential failure, was replace to correct the problem 4. Fortunately the person following me was not tailgating so no accident.