Hello. I have a 2017 X3 3.5XI with the M-sport package which has 55,000miles on the clock. My BMW dealer recommends I change both front/rear diff and the transfer case fluids. I only drive 3000 miles a year in this vehicle now I'm semi retired. I'm not experiencing any problems with any of these components; gear changes/all wheel drive functions are still smooth and quiet; no vibration etc. What are your recommendations on flushing/replacing fluids/oil based on vehicle age and the amount of use they get based on your own experiences? Thank you. Moman