Transmission because I never checked the fluid levels.
The 1964 plymouth belvedere is a great car, it took a very hard beating.
These cars are awesome. My dad owned a 63 four door, and it was one hell of a ride. It easily did 85mph to the supermarket, and the engine sounded like it was idling at that speed. Not to mention the ride was so smooth and comfortable that you didn't even notice that you were going that fast.
Long live big old American cars!