My vehicle is a 2004 2500HD Duramax 4x4 with 260k miles. Over the last eight months have installed five sets of new rear brake calipers consisting of two sets of AC Delco calipers, one set of Raybestos, and one set of PowerStop, all purchased from RockAuto. Each of the first four sets failed in less than 500 miles, pushing fluid past the piston seals.Last week the local Chevrolet dealership service and parts managers recommended a set of GM OEM rear calipers. I did and in less than 150 miles, both OEM units are leaking past the seals. Prior to the 1st installation, the system was completely flushed and new DOT4 fluid added. Have since flushed the system a 2nd time and added DOT3 fluid. The brake light and ABS light illuminate when the ignition is activated and go out in a couple seconds, as usual. No codes show up. The brake lines all appear good. There is no noticeable change in braking behavior like lockups or pulling. Discovered some warpage this morning in the rear rotors and had them turned. I had not felt any vibration during braking and doubt this could be the problem. Thanks for any assistance.