At approximately 37500 was in the dealer for a oil change. Service advisor came out and told me, I needed new brakes on the rear. I thought boy not many miles on the truck so I asked if I could see them-just to make sure I wasn't about to take one in the rear. Looked at them, and gave the okay. About 15 minutes later he was back, saying the piston caliper was cracked. Went back took a look --two deep cracks about an inch apart. Talked to mechanic-he stated not the first one he's seen on new F150'S. Mine was the driver side rear. Turned out to be an expensive oil change!