1996 bonneville transmission problem

I had a neighbor once who had a very steep driveway where they parked there van every night. I do not know much about transmissions, but I was told that cause the guy never used the emergency brake, the transmission was holding the van in place on the steep driveway (cause the tranny was in park, obviously) and eventually something inside broke and the van rolled back down the driveway. I do not know exactly, but I do know that my cars have never liked being held on a steep driveway by just the trans and not the e-brake.

Someone who knows what they are talking about will chirp in soon I bet.

Thanks,but my driveway is steep coming up the hill, but where I park my car is level.I think something got knocked loose when I hit that rock,hopefully that's all that's wrong.

also, the gear shift moves forward & backward without holding in the shift lock,but when it does want to go back in gear, it won't slide back & forth without holding it in.