The transfer case oil replacement is a good thing to do. It's not expensive and not difficult. Get the right oil from bmw, drain it, fill it, reset it (so the car knows when to shout at you for service. doesn't seem to affect performance though if you don't reset it).

I did this recently and the car runs smoother, and no worries about that bloody thing going bad suddenly. Afaik the thing is good untill the lights come up, so you could be just in time.



Same for the gearbox, get the set (oil, pan-filter, bolts) and replace the oil. Makes gearchanges smoother


both actions resulted in a much better, smoother, behaviour. especially notable with a cold start in the morning.



I had no fault messages at all but the oil was definitely far from fresh (X3 140.000km, X5 170.000km)



Don't expect too much from the fault codes, many times they are merely pointing at some symptoms, not causes.