99 Durango - Rear brakes NOT working.....

For a few weeks my 99 Durango has been only braking by the front two brakes which as some of you may know is very scary because stopping this tank is next to impossible without all 4 brakes working properly.

I 'assume' the rear isn't working because when I brake, the front wheels just lock up while the rear is still rolling.

The wierd thing is that the front lock up even when the slightest pressure is applied to the pedal.

Can there be a problem with both the front and the rear brakes??? Could something be not operating correctly causing the front brakes to lock and nothing to the rear brakes?

I was just going to buy some rear shoes and open up the rear brake drums but if any of you have a different suggestion, please help. Thanks

Reasons why your rear brakes may not be working.
Out of adjustment.
Leaking wheel cylinders.
Damaged brake lines.
Deteriorated flex line to the rear.
Pressure imbalance in the system has closed off the fluid to the rear.