Check the vaction pictures for that year. the auto trans uses a computer controlled clutch to engage the rear drive shaft to various degrees. The system is front drive based but you should still get some spin in the rear. If the wire or wires have are not connected to the clutch pack it will not engage and could go 100% front. The system has changed a bit over the years but the general functionality is the same, that is when you should check the pics for your year. The clutch pack could be dead but you should still be able to test voltage to it.
Hope that helps.