Cadillac: 91 seville 4.9 trans/drivetrain problem, output shaft, rear brakes

Question
i took the wheels off and was able to spin them in neutral. any idea what is locking up  when car is on the ground? isnt there a pin or something that engages into the outer teeth of trans when park is engaged and could this pin be electronic? thank you for your time! -------------------------

Followup To

Question -
seville wont roll in neutral.  the wheels are locked up all the time. i can hear trans. go  into gear when shifting but cant take off.  ive checked front and rear brakes for froze calipers and also if i rock the car back and forth in drive some times it breaks free and will go forward when applying gas. any ideas ? lockup torch converter?  bad sileniod?  or something with ABS brakes?

Answer -
Jack it up and see if all the wheels will spin by hand. If they do then you most likely have a trans problem. If they don't could be stuck calipers. Take the tires off and see if you can pry the pads away from the rotors.

Is the emergency brake OFF or rusted ?.

Answer
Inside the trans thereis what is called a PARKING PAWL that locks the output shaft of the transmission when it is in neutral.

But it is mechanically driven and I have never seen one stuck. But anything is possible.

Your going to need someone who can physically inspect the vehicle for you to find the problem, Since obviously I can't do it from here.