Flood damage can occur if the permissible fording depth of a vehicle is exceeded. Ingress of water can cause damage to the engine (water shock) or components.
Because dirt particles generally enter into the component with the water (e.g. starter motor, wiring harness), the components need to be thoroughly inspected.
Residual moisture in the components leads to corrosion (increased contact resistance in the component), which can lead to a component failure at a later time.
If water ingress into the electrical components cannot be ruled out, it is recommended to replace the component to ensure correct functioning through the vehicle lifetime.
BMW X3 Service & Repair Manual > Front axle gearbox: Removing and installing/replacing front axle differential
IMPORTANT:
For the initial filling of a new replacement front axle differential, the gearbox is filled with 600
ml oil! If oil is filled up to the lower edge of the oil filler opening, the gearbox would be
overfilled and in rare individual cases oil could emerge from the ventilation opening ...