Navy-maybe you missed it in my post-you don't need to move the front calipers to the rear to see if they work proving that your rears are the culpred---just change the lines at the master or combo valve and then see if the fronts still work-that will prove/disprove wether its calipers or master issue. However, since neither rear works now, its probably something thats common to both that is wrong and if when you hook the fronts up you'll prove it.