Got the company truck service today and they said the transfer case oil was burnt. Lots of highway miles and I do use 4x4 in the winter and on the gravel, I use 'auto' sparingly- I either want 4x4 NOW or 2wd is fine. Is there an issue with these cases? I do look after my gear as the out of the way places I go may be inconvenient for a breakdown. 2019 K1500LD, 5.3L auto.