@whitefaceford: Skipping Differential Service Can Cost You $12,000 This sludge inside a rear differential is not normal. This truck had around 70,000 miles and had never been serviced once, and now it's looking at a full day of labor plus three hours of hot water washing just to get clean enough for a solid repair. When did you last check your differential fluid? #FordMaintenance #DieselTrucks #SuperDuty