95 Cavalier

The problem could be at the master cylinder or somewhere in the front brakes. The reason why I say front brakes possibly is because with a street car you should have 70% of your stopping power at the front brakes. If for some reason your pressure is reduced at the front brakes then naturally the rear will taxed with the full load. Jack the car up with all 4 wheels in the air and have someone ease into the brakes. The front should come in first before the rear. If the rear comes in first then the proportion of pressure is not right. There are only so many things that are responsable for proportioning the pressure and they are all located up front. I would start at the master cylinder.