the trans is not rebuilt in the car... what happens is you can disassemble the transmission piece by piece from the car.
Reverse the order to install parts.
this was a method used in first gen T-bird cars.
Makes no sense to do this method on a car where the trans can be removed in one piece
Some people are like Slinkies... Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs.