This anonymised case is based on a BMW xDrive investigated at BEM-TEC. The illustration does not show the customer vehicle.
The symptom was most noticeable at low speed
The car jerked at walking pace and while turning. We begin with the basics: tyre sizes and wear, all-wheel-drive fault codes, and transfer-case service and adaptation data.
When oil service and calibration do not help
In this case, the transfer-case oil had been changed and adaptation values addressed earlier. Another calibration did not remove the symptom either. When the basic causes have been ruled out and the symptom remains, mechanical wear in the transfer case may be suspected.
Repair decisions follow the evidence
With an xDrive symptom, it makes little sense to jump straight to an expensive replacement. We first check the tyres, other possible drivetrain faults and how the symptom behaves in different situations. Only then can a transfer-case repair or replacement be justified.