Crate Training a Puppy?

I have a 7 month old Ridgeback Mastiff Pit Bull mix. He is fully potty trained, but poops and pees in his crate daily. The crate is the right size for him as he is big. But he will poop and lay right in it. It doesn't matter how long he is in there he poops. I have tried one of my t-shirts, I've tried nothing in there, I've put his dog bed there, and he poops on it. What can I do? I have two other dogs that are 4 years old and 3 years old and aren't in crates and I never had this problem with their crate training.