Rear

The Emergency brake on my 2001 V6 Mustang (ABS not equipped), doesn't seem to work properly. If I pull the E-brake while in motion, it doesn't lock up the rear wheels. It doesn't even hardly slow the car's forward momentum. I changed the pads and rotors all around (I have rotors on the front and rear), but that didn't fix the problem either. I have to press the brake peddle very hard to get the rear brake pads to engage their rotors. In icy conditions my rear wheels will push my car while the front wheels are locked up. I have three questions. Is this normal? How can I fix this if it is not normal? And, is there a way to adjust the pressure applied to the rear rotors by the E-brake?