As I brake the peddle starts out good but as I slow and let up a little to coast, when I re-apply to complete the stop, the peddle goes to the floor. Before this started I found a leaking rear brake cylinder so I replaced both rear cylinders and shoes and front pads. I have bled the entire system very well and this is still happening. I have went exactly by the book on bleeding the brake system. Two things that the book shows that my truck don't have is the pin that has to be pulled out to bleed the front calipers and I don't get brake fluid out of the bleeder screw on the differential valve.