Ok just got back from my scheduled oil change from jiffy lube. They checked the truck over and suggested that the rear diff fluid be changed as it appeared burnt. Truck has 26555 miles on it. I just put a hitch on but haven't used it yet. It was a rental before i bought it and had 24000 on it. There was obviously no hitch on it before i put it there so It hasn't towed anything heavy. The fluid is definatley much darker that the fluid in the front diff. After reading some post on here about people having thier rears replaced early I'm starting to get worried. There is a slight clunking sound when switching from D to R or vice versa. Should i just change out the fluid or should i be having the dealer check things out?