First question here but I recently purchased 2014 King Ranch with 145k miles that has the appearance of being well taken care of. Previous owner relied on a quick-change lube for regular maint. Besides using an oil filter not even specified for any Ford they put gear oil in the differential instead of automatic transmission fluid. According to Car Fax it was changed at 79k miles. PO said it was his wife's vehicle and she never towed so I was wondering why it was changed so soon. Did they put in a heavier fluid to cover up another issue or just grabbed a jug of the first gear oil they found and put it in. I went ahead and put in the specified fluid and no issues noticed yet in a couple hundred miles. I didn't see any threads here about a common issue with the differential, so I was wondering what you all think.